New 380sl owner

I just traded my old Coleman camper for what I believe to be a pretty decent '85 380sl. I am looking for a good place to possibly buy some engine parts. My car runs and drives but has a lot of miles, 334,xxx, and it smokes. I'm trying to decide if I want to rebuild the engine or replace it. I am also interested in whether or not I can replace the current 3.8 v8 with a larger v8 from a different model MB. Any info would be greatly appreciated.