I've decided to go with an M42 out of an E36 130k miles, assuming the odometer works. The seller is throwing in the transmission as well...although the transmission isn't a direct fit. I think using that transmission will require a shortened driveshaft and a few other tweaks. At the very least, maybe the shifter will have a shorter throw (the Pelican Parts 101 Projects book has a good list & reference) and hopefully better bushings I can use. The shifter in my car felt pretty worn. I'm surprised at how much even complete bushing kits on Pelican Parts sell for. Maybe I can just identify the worn bushings and replace them.
The To-buy list starts as follows:
Oil pan gasket upper & lower. The bolts in the sump can back themselves out and can only be accessed with the engine out. Pretty sure this is also required since I'm using the E30 oil pan.
Valve Cover Gasket: It appears the timing chain gear and tensioner can be checked with only removing the valve cover gasket. This appears to be something that wouldn't be much harder to do with the engine in. I've ready to check the sump for pieces of chain or tensioner.
Timing Chain and Tensioner: I suppose this will depend on the inspection.
Hoses: I'm on the fence about the "mess under the intake" solution. I'll have to read-up on it again. The hoses looked to be in reasonably good condition...although it's probably good insurance to replace the ones that are difficult to access...I also feel pretty confident I can put it back how I found it.
Engine Mount: Engine support has a hole in it. I'll double-check all the rubber engine and transmission mounts.
Anything else I should be thinking about?