I have a 68 firebird convertible with manual drum brakes. I want to convert the front to power disc. I have a few questions. 1) Who makes the best disc brake conversion kit? 2) Do I have to get rid of my 14 cragers and switch to 15x7 rims and tires? 3) does it matter if I get a 9 or 11 inch booster as I am concerned my valve covers may get in the way? Anything else I am forgetting?