Big Block Swap?

Hello all. My dad recentally aquired a 91 1/2 ton. He wants to do some work to it to make it pretty quick. He owns a logging company and the man they are logging on has a junk yard. He found out that the man has a truck with a 454 in there. He asked me about swapping them, I am knowledgable on OBD II systems but not with OBD I.
What I am trying to find out is, assuming the 454 is also throttle body injected does the wiring haness need to be swapped to or can it be adapted to the big block. I know the ECU has to be swapped either way.
I am unsure of the year of the engine or what type of injection it has just yet, I wanted to find alil info out before I go see what all we need.
I know if it is any other type of injection (MPI, SFI) the harness has to be swapped.
Thanks in advance

well my stepfather has a 88 chevy 1/2 ton so I know the truck well if you want to convert a small block truck to a big block you might have to change the plug to the throttle positioning sensor and change the computer as the computer as the computer controls fuel flow to the motor a 454 is going to need more gas to idle than 350 and i could be wrong but i believe the 454 also has a larger tbi system needing the 454 computer also these trucks have a thing that the motor mounts go if you beat it so i would change them during the swap if it were me i would also change the tbi system and make it either carbureted or do a MPFI system our 88 we have been fighting a losing battle with electronics for years with the junk tbi system

You don't say which sb engine is currently in your truck, but the easiest is to switch everything. Just unbolt the computer wiring harness at the firewall and leave everything connected to the engine. Fish out the computer c/with the harness to the firewall and viola, you shouldn't have any headaches. As far as trying to adapt one harness to the other, most things may be the same but a BBC is just that; big. I'm not sure about this, but some of the sb wiring may be shorter than the bb harness.

Sorry about that, it has the 5.7 (350) engine in it currentally.

I think the main reason he wants to do this is back when they first came out he bought a new 454SS, and he wanted it manual so he sold it hoping to do what he is wanting to do right now. So now he wants the 454 with the manual.
The 454 he is getting has a auto, and from what I have read (unsure) they only come in auto. next logical question is will the automatic wiring harness and ECU control the manual setup.


Sorry about all the questions. I am knowledgeable about OBD II setups and could do this without problem, but I have not had much experience with OBD I setups. Thanks for all the help so far.