Author Topic: K10 frame boxing for towing  (Read 1766 times)

Offline berserk

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K10 frame boxing for towing
« on: January 31, 2022, 03:07:37 AM »
I would like to buy or build a truck capable of towing at least 10,000-15,000 pounds and 4wd. In my area K30 dually's are beyond rare and I have only seen one in person in 25 years of driving square bodies. (It's completely mint and surprise it's not for sale)

Right now I have a 76 K10 small block and have considered potential upgrades to make it more capable of towing heavy. I know the biggest difference is the frame, as I can just axle swap for bigger brakes and more wheel studs. I have seen frame boxing kits typically used for crawling and I have consider the possibility of using it to beef the frame up for towing heavy.

It seems to me that what my frame lacks in thickness and strength compared to the k30 would be more than made up for if it was boxed. Rigidity, torsional strength, load rating may all be improved. And then of course I would swap the axles and run air bags in the rear.

Does anyone have an opinion on this proposed upgrade and it's effectiveness for strengthening the K10 frame to be at least as strong as a k30? Any other thing I have over looked regarding the chassis that would need to be addressed to tow heavy with this truck?





76 Chevy k10 350/th350/203 part time. Vortec head 350 Dana 60 w/Detroit, 14 bolt Tru Trac, 33" Micky T. Mudders.

Offline JohnnyPopper

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Re: K10 frame boxing for towing
« Reply #1 on: January 31, 2022, 02:30:49 PM »
Hey Berserk, that is quite a challenge.

When you say box, do you mean closing the open side of the C channel of the frame?

I would think that inserting a smaller C channel inside the frame might add more rigidity.

I would look to see where in the frame torquing is occurring and start there.

You didn't mention what transmission you have. If Auto you should move to a TH400. What CID does your small block have?

I've got a 89 C30 with a 454/TH400 HD package, factory tow package I might be talked out of.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline berserk

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Re: K10 frame boxing for towing
« Reply #2 on: January 31, 2022, 03:27:14 PM »
Hey Berserk, that is quite a challenge.

When you say box, do you mean closing the open side of the C channel of the frame?

I would think that inserting a smaller C channel inside the frame might add more rigidity.

I would look to see where in the frame torquing is occurring and start there.

You didn't mention what transmission you have. If Auto you should move to a TH400. What CID does your small block have?

I've got a 89 C30 with a 454/TH400 HD package, factory tow package I might be talked out of.
RobBonneyFab.com has a kit, it caps the back side of the C channel to completely box in the frame. I don't know much about the kit or maker but it looks user friendly. I would link the site but it's be around 4 years since I posted and can't remember the rules about links.

I have a vortec head 350 and Th350 trans. I realize these would lack but I just wanted to get an idea of the chassis would be able to handle it before I worried about any drivetrain work.

I have just been getting fed up with the truck search, there either clapped out, too much(for me anyway) or to far away. In desperation I have been day dreaming about using what I have which is the K10.



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76 Chevy k10 350/th350/203 part time. Vortec head 350 Dana 60 w/Detroit, 14 bolt Tru Trac, 33" Micky T. Mudders.

Offline JohnnyPopper

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Re: K10 frame boxing for towing
« Reply #3 on: January 31, 2022, 03:53:21 PM »
I get it, sounds like you may end up with a beefed up K10 for less than you would pay for a K30.

Capping the open face of the frame will certainly add to rigidity, I think lining the channel would exceed that.

1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Mr Diesel

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Re: K10 frame boxing for towing
« Reply #4 on: January 31, 2022, 04:01:56 PM »
Trying to beef up your 1/2 ton truck to 1 ton capacity will almost certainly cost you more in time and money than if you just bought a heavier truck. Not worth it in my opinion.

There are parts of the U.S. where K30 trucks can still be found cheap. Craigslist and Facebook marketplace have deals all the time in my State. I would settle on a 1990s K30 before I tried to convert a square body. The 1990s models are priced cheaper than square bodies in much of the country right now. Take a one week vacation to rural Texas and drive home another truck.
1976 C20 Crewcab, 6.2L/SM465
1982 K30 Crewcab , 427TD/TH400
1983 C30, 6.2L/TH400
1983 K30 Crewcab 454/700R4
1986 K10 350/400. 1989 K30 cab/chassis 454/SM465

Offline berserk

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Re: K10 frame boxing for towing
« Reply #5 on: February 01, 2022, 01:56:10 AM »
Trying to beef up your 1/2 ton truck to 1 ton capacity will almost certainly cost you more in time and money than if you just bought a heavier truck. Not worth it in my opinion.

There are parts of the U.S. where K30 trucks can still be found cheap. Craigslist and Facebook marketplace have deals all the time in my State. I would settle on a 1990s K30 before I tried to convert a square body. The 1990s models are priced cheaper than square bodies in much of the country right now. Take a one week vacation to rural Texas and drive home another truck.
I haven't been wrenching much because of previous injuries but was in the shop yesterday for a while. Fired up the old K10 and pulled it out and came to the same conclusion as you at this point. I started realistically thinking about all the Fab work and decided against it. I just don't have it in me to start a 6 month or year-long project again which is what it will end up being as I work slow and methodical and I'm alone in the shop.

I'm out of Oklahoma and have been looking at Texas trucks, it would be tough though to make the drive down there to find out the owner lied about the condition. But buying a Texas truck is what I'm considering at this point unless I run across one in OK.


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76 Chevy k10 350/th350/203 part time. Vortec head 350 Dana 60 w/Detroit, 14 bolt Tru Trac, 33" Micky T. Mudders.

Offline JohnnyPopper

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Re: K10 frame boxing for towing
« Reply #6 on: February 01, 2022, 09:46:47 AM »
There are parts of the U.S. where K30 trucks can still be found cheap. Craigslist and Facebook marketplace have deals all the time in my State. I would settle on a 1990s K30 before I tried to convert a square body. The 1990s models are priced cheaper than square bodies in much of the country right now. 
[/quote]

Yes, but they certainly don't look as cool  8)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction