Neither are really smart for an out-of-the-box B27, but what you can do, and what sounds like a lot of fun, is do a head conversion with an M20B25 (stroked 2.5, basically), and then your compression would drop to a hair below 8.0:1. That's a pretty nice number for forced induction, and it's what a lot of the better-off E30 owners are doing these days. Man
I want a head swap. Here
's a list of some parts you're going to need anyway.