I put a dual mc/ booster in a 59 gmc. The unit did interfere with the park brake. I repositioned the park brake pulley back about 4 inches and it worked fine. Don't know of any clearence issues with the 3 on the tree... mine was a late model 4 speed. this set up does push the master cylinder way back... almost under the seat. it makes it very difficult to service your brake fluid. you will probably have to put new brake lines in for the conversion