s50 and m50 and m52. For a harder swap you can stick in the v8 from the m5 if you have that kind of cash and experience. You can stick in a small block 350. erm... thats the immediate ones i can think of.
Good luck with the e34 but i highly doubt you will push 300. At least if its a 525. The m20 is only good for about 270 hp max with a street runnable set up.
<span style='font-family:Geneva'><span style='font-size:14pt;line-height:100%'><span style='color:red'>Fox</span></span> <span style='color:gray'>the Pirate</span>
Diplomacy is saying "nice doggy" until you find a rock.</span>
I live my life one quarter mile at a time, and for those 23 or more seconds I'm free.