Trying to figure out Engine Size

[SoEasilySwayed]

This might be a dumb question

I'm trying to figure exactly what engine is under the hood.
This truck used to be a diesel, but was converted.
The VIN says its a 454, but, I think its smaller, and I know its not going to be the same engine...

This is the info I got from the VIN:
Division: GMC
Chassis Type: 2 Wheel Drive
Engine Description: 454-4 V8
Series: 10
Body Type: Pick-Up
Year: 1979
Assembly Plant: Fremont, CA

Is there something/somehow I can check on the motor? Like Engine ID/Serial #?
It's still in the truck.

ALSO. The Fender Emblem says High Sierra 1500. Is that like the Chevy C15 or C10?
I know GMC/Chevy are the same, but I want to know what chevy parts I can work with if I go to the junk yard...

[zieg85]

C10-Chevy 1500-GMC equivalent.  On the block behind the alternator is a number that can be decoded as to what it is and its original application

[zieg85]

Here is an example of what to look for assuming it is a Chevy engine

[SoEasilySwayed]

Oh great! Would the alternator have to be removed in order to see that? if its there?
Im going to be looking this weekend and ill let you know how it goess

[enaberif]

Pad behind the alternator is not always accurate though its a good spot to get started.

Look at this area to find a number which will give you a better idea:

[SoEasilySwayed]

Thanks @Enaberif Ill look for that too!

[Blazin]

Pad behind the alt. is the best bet. Van tell you what the engine is, even what it came out of, Car truck etc.