What engine for an 82 380sec?
 

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.

The problem this particular engine has is likely a failed timing chain tensioner or broken chain guide. That can be fixed for about $100 ( in parts), but will shortly lead to the timing chain jumping teeth and breaking if neglected. The 81-83 380 engine came with a weak single row chain- the 84-85 had a double row ( many earlier ones were upgraded, though). Do some research on M116 and M117 timing chains...

I really don't know how "swappable" the other engines are. The fuel systems are all different- the basic blocks are the same. My guess- only a guess, is that a euro 380 would be fairly easy, next would be a US 420 (both M116s)

The 1986-91 4.2 engine is the best & easiest swap.

It is better to use the intake manifold from the 3.8 engine.

I too would drop in the 4.2L for ease of install. Hell, stock for stock you are gaining nearly 50hp!

Also, look around for the euro dual logs while it is apart. Bump the power up a bit more while it is all apart.

If the engine is not dead, STOP running it, and convert/repair the chain! Then no swap is needed!