What engine for an 82 380sec?

[Travis_k]

This car has sat for a while, and I could likely get it really cheap, like cheap enough it would be worth fixing, but I think it will need a new engine (it starts and has good oil pressure, but has a loud rattling sound from the front of the drivers side head. I could get pretty much any long block from pic and pull for cheap (us or euro 3.8. 4.2, us or euro 5.0, or a 5.6, and the 3.0 6 or a diesel). Are a lot of parts different if I wanted to put a 5.0 in it? Or would a newer 4.2 be easier? I dont really want to put another us spec 3.8 in it, but anything else would be an option. The less related parts i have to buy the cheaper it would be though. If it is pretty much the same, I would prefer using a 4.2, but i dont know how many other parts from the donor car i would have to use.