Well, after chatting with everyone on what to do about my engine situation:
I decided to tear into the 3.8 I have and check it over. So that’s exactly what I did:
I found my bottom end rattle along the way, the number 5 rod bearing was almost gone:
We figured out that due to the engine sitting for so long before I got it, it ended up dry starting the first time, in turn destroying the bearings.
Outside of the destroyed rod bearing on one cylinder and slight dry wear on the rest, everything looks excellent.
I measured all the rod journals, they are all dead on with no sign of wear. The Main journals are all dead on with no sign of wear as well. The cylinder bores are still perfectly in spec, they’ll just need a quick hone to remove the crap from sitting. I still have to remove the camshaft and inspect the journals there, but initial inspection is proving very worthwhile.
Assuming I don’t find anything major with the camshaft (judging by what I can see, all will be well), I should be just a quick rebuild away from having my 3.8 back in my van.