RB:

The engines in the US spec 380SLs are very much limited by the low compression ratio of 8.3:1. While a change of valve timing will bring some improvement, the word "hot" would not occur to most folks.

That said, cams of code #s 70/71 or 04/05 (left/right) will be better than the 62/63 or 68/69 that are the usual US spec cams.

And, if you are considering the use of heads from an iron block engine (3.5L), they do not directly bolt on.