My e30m50 brake booster dilemma. need advice!

[adamnitti]

I just purchased an e30m50 track car a couple weeks ago, and I discovered that my brake booster was bad and had to be replaced. The gentleman who did the conversion on the car I now have told me that he ended up using a brake booster from a 320 because it allowed for more space in the engine compartment. So, I found 2 working 320i brake boosters from salvage yards and proceeded to do the swap. Unfortunately, both of the boosters I purchased are almost 2" bigger in diameter than the one that came out of the car and will not fit without coming into contact with the intake manifold. This contact with the manifold is subsequently causing vibration to be transmitted into the cabin. Now I am wondering if the original one used in the conversion really came from a 320. So.... my question is this: Do you know if there is a BMW brake booster available that is smaller than the 320's? The old one I have still has the ATE part number on it, but ATE no longer lists that number as an available part. So, I have no way to figure out what the heck this booster was originally built for.

Thanks in advance for any tips or suggestions!!!