Hey,
I did a SBC swap on my 87 Cutlass 20 years ago and I’ll post what I know about the swap. I had the entire process documented in a post on oldspower.com but the old forum there is gone.
First I wanted to share my opinion.
1) It’s your car, do whatever you want, or whatever is right for you. The more I think about it though, I wouldn’t do the swap on a
Hurst/Olds if it were my car because it think it will hurt the value.
2) I believe any collectible G-body needs the original OEM parts to maintain top value. It needs to look OEM under the hood. That means matching block, original E4MC carb, emissions components, A/C. Etc. i think even stock block cars with all the emissions ripped out with a Holley will take a hit on value. If I had a GN, turbo Buick,
Hurst/Olds, maybe a clean 442, I’d save all OEM parts. My 87 Cutlass? Not so important, dime a dozen, not collectible in my opinion.
So, if you want to swap, I recommend removing the 307 with everything intact, ECM, harnesses, all emissions, A/C, condenser, mounts, everything. So you can put it back someday. Just my opinion.
Ok so for the swap. I used a 87 Monte Carlo donor car so I had everything. I am running a Chevy 355 with E4ME carb and ECM, with all emissions intact except for EGR.
You need to swap:
engine frame mounts. 2004R should be dual bolt pattern for Chevy or BOP but you need to check.
All engine accessories. Alternator and AC are on opposite sides usually. PS pump, pulleys, brackets.
AC-compressor is on opposite side. You would need a Chevy condensor and lines to do a clean swap. Might need the compressor too, not sure.
Body wiring harness on drivers side will work but I swapped to the Chevy harness so wire length and connectors were all there. ECM wiring harness will not. OEM carbs are different. I wouldn’t run the Olds carb and ECM on the Chevy for many reasons. If you’re going aftermarket carb and no emissions then save everything. Everything, so you can go back to OEM someday.
Exhaust headers/manifolds obviously. Save the Olds stuff including the little emissions bits.
Battery. Olds in driver’s side, Chevy is on passenger side. I swapped the battery location so that all the Chevy wiring could be used without mods. Fortunately most Cutlasses have dual battery trays thanks to the diesel experiment in the early 80s. Also swapped the charcoal canister to other side, including the vapor line to the fuel tank that runs under the engine along the crossmember.