I bought a 4 wheel disc brake conversion kit from CPP:

http://www.classicperform.com/camaro.htm

but I purchased it through Matt's Classic Bowtie:

http://mattsclassicbowties.com/en-us/dept_30.html

It's a COMPLETE kit. The only thing I had to reuse is the steering arm knuckle off each drum, part #37 in this picture:
http://www.1968firebird.org/illustrated/front/front1.html

Total price for the front only is $729 through Matt or $799 through CPP. It's a great kit if you don't want to screw with trying to find all the correct pieces in a junkyard/part store, etc. They are stock GM brakes so replacement parts can be found at your local parts store.

P.S. Have them add the 11" booster at no extra charge.