The swap has been done, many times over Here are a couple sites that might help
http://www.e30m50.com/mym50swap.htm http://www.terrysaytherauto.com/E30-S52Conversion.htm
I saw a turbo s50 swap at Bimmerfest East in a Blue E30M3 widebody.
Whoever's that was probably could help you out.
Here is a photo of the engine bay of that turbo swap
