Depending on if your going to run a carbed or EFI engine, it depends.A carbed 350 takes all of 5 or 6 wires to get it running (power to coil, hook up the alternator, the starter, temperature gauge, and oil pressure). So you would need to find the corresponding wires on the 240sx chasis, and throw the rest away. So theres the wiring part. EFI, well, your on your own. As far as transmission, don't go turbo 350. With the ratio's with that and the 240's 4.03 or whatever rear-end, you'll top out at somewhere around 90 mph unless your small block revs to 12,000. Lining the driveshaft and stuff up, uh, put the engine in and start measuring. Make mounts accordingly. A good site though for engine swap stuff is
http://www.hybridz.org. It's all about the v8 in the 240z chassis, and the people there are knowlegeable about this stuff.