what about the vvc k series engine (later 160 version 157bhp) much lighter than other engines mentioned and go well especially in a lighter car. all you have to do is make sure you get rid of the o.e hg and fit the land rover mls hg job done

 

donor e36 bmw are cheap as chips these days maybe one of the superb straight six engines would do the job

 

Thought about a 318is engine and box. The 6 pot is a bit heavier than I'd like but would sound nice, my old e30 325i went well and that was the m20 engine...