the brake booster can always be relocated, or you can used 2 smaller ones instead. a friend of mine is swapping an m50 into an e30 at the moment, the brake booster had to be moved for throttle body clearnace. he's gone for twin smaller boosters located on the other side of the engine bay.
i think itb's would have a useful effect on an m20 only if already had its tits tuned off. i know of a 2.7 stroker over here with itb's but thats running almost 300hp at the crank so i think that was worth while doing