Advice wanted - maybe unique situation?

[M3Gonz]

Hey all, I guess this is my first post!

Here's what I've got going on, I have a couple E36 M3's and know that car fairly well, but am new to the E30 scene. One of my E36's just recently got wrecked and it's not fixable (thanks alot cell phone distracted driver), best we can do is salvage what we can out of the car which includes a 400,000 mile (yes I'm serious) S52 engine. As far as I know the engine has not ever been rebuilt, but it was in dire need of it anyways.

I have been looking for a decent E30 to pick up and drop the S52 into after we rebuild it. Turns out, I got a decent deal on a local '89 325i that already has an M50 swap about half completed. The seller ran out of motivation and funds and was relieved that the car would be going to a good home for a fun father/son project.

Here's my question for you all: Other than the tune, is there anything different about finishing the M50 swap than what we'll need to do for the S52 swap? The S52 has an M50 manifold on it already. Does the new oil pan that's on the M50 also fit the S52, and will the exhaust manifold that we need to find for the M50 also fit the S52?

Reason I'm asking is that my father-in-law thinks that it makes more sense at this point to just finish the M50 swap (by the way, he's very smart but not a BMW guy and will be helping a lot, we're working out of his heated 10,000 sq ft machine shop) and get the car running if everything is essentially the same for the M50 & the S52. Then once we have a running car we can take our time rebuilding the S52, then have a much easier time dropping that in at a later date since everything else is already done. All we'd need to do at that point is change the engine tune.

What are your thoughts everyone?

Thanks!

[M3Gonz]

Here's the unfortunate donor car for the S52, and below is the E30 we picked up with a half completed M50 swap sitting in it.

[Northern]

Exhaust manifold should fit fine. Depends on what the swapped e30 has now. If it's the stock M50 cast manifolds, You should be able to switch to the stainless S52 ones, which are supposed to be better (SAP delete plates aside).

Oil pan will fit if you swap the pickup tube/dipstick (will need to mod it for CCV oil drain). If the E34 M50 pan on the swap has the built-in windage tray, I'd remove it and run the one on the S52 block.

Brakes/booster solution should be good to go, if it fit the M50, it'll fit the S52.

Wiring will need to be redone to use the OBD2 harness/ecu (either rewire it or buy an adapter), and the ECU flashed to remove EWS and whichever emissions bits you aren't running.
There's a ton of people offering the flashing service, or just selling ECUs with deletes done. Alternatively it's like $40 for the cable and MS41 quickflash - just that there's a lot of reading involved if you DIY.