If you have more length to play with and you can't quite fit the booster because of the diameter - consider a Hydroboost. It runs off the power steering pump instead of engine vacuum. It is quite a bit more compact diameter-wise, and can supply more than enough power to operate 4 wheel disc brakes.
You could also use a remote mount brake master cylinder and booster by using the stock master cylinder to operate a slave cylinder. The slave cylinder would operate the remote mount brake system.
