Hey I just picked up a 1983 D50 with a 4d55 in it. It needs a few things like a new radiator and other little things. I have been reading up on these motors and I saw something about putting a 4d56 head on it. I was looking at them on ebay but not sure which one to buy. Also what are some other performance things I can do to it to get a little more power? It feels like it takes years to get from 0-60.
I would also like the rebuild the motor at some point but cant find parts anywhere but ebay and I would like to stay away from Chinese stuff. Any help would be greatly appreciated.

Thanks so much!