help swap AC to heater

[Destro]

Has anyone done this before? Have any tips??
I'm going to be swapping cabs in the spring and the new cab has AC, the old one does not.

 My plan is to weld all the holes shut on the firewall,basically smoothing it, and then trace the old non-AC firewall holes and cut them out. If I do this, the old heater box should work,right??
I know someone must have done this before
Thanks

[VileZambonie]

Why not just use an AC delete box this way you can always run AC again if you want? http://www.acdelete.com/pages/73-90_Truck.htm

[beastie_3]

The AC delete box is a good setup. I have mine all mocked up and ill probably finish it this weekend.

[Destro]

I really didnt want to use the delete plate. Cost is a big factor. I figured my welder is paid for and I have sheet metal,so I'd just be out my time. Plus the AC cab is missing alot of key AC components and my heater only set-up has a brand new heater core in it.

Does anyone know if there is a difference in the 2 cabs other than the holes cut in different places. It looks to be the same to me,I'd just feel better hearing from someone who has done this.