Re: 3.0 1 piece rear main to 2 piece rear main question
Flywheel, yes, also the coupler and starter.
For internals, the 140HP has 2 rod bearing options, and it would depend on what 140 crank you got and what the 3.0 uses. Not sure if the rods are different, or just the rod bearings on the 140. The fuel pump hole is different between the blocks and the 3.0 pump I put on my 140 barely hits the gasket surface on the bottom,,, it hasn't leaked so far. The 140 is a low compression engine compared to the 3.0, something like 8.5:1 compared to 9.3:1, this could just be the 3.0LX though. The head should fit no problem and the newer small intake runner is better, so I'd stick with that. I'm not sure of the head CC's between the 2 engines, that could account for some of the compression difference between the 140 and 3.0. I think you should talk to a machinist or search through a bearing and piston catalog to see what the P/N differences are.
If it were mine, I would keep looking for a 1 piece rear main seal 3.0 block.
