Hello,
lots of good advice so far! As Jordan said, the "weakness" of the B230 engine is most likely only an issue if you plan to take out about 240 or more hp...
Btw, the only to do this is turbocharging. I suppose your rules does not allow turbos? If they did - that would be way cool :)

I wouldnt foresee any problems with 150hp in a well balanced and otherwise healthy B230E.
Use the 531 head, or if you cannot find it, the 405 head. The K cam or the VX cam is probably best (as pointed out by another poster, the turbobricks site have a good cam comparison). There are harder springs available, or you can fit double springs. If you plan to mill the head, you should use adjustable cam gears. Good to have anyway, if you want to finetune the torque curve.

Have fun! /
Jakob