The C5 brakes should only affect your rim size, but you're already at 17, so as long as those clear....
Here's my combo:
Belltech 2" drop spindles for 99-04 Blazer
Powerstop pad and rotor package
Reman Blazer calipers
Moog 5662 springs
KYB Excel G shocks
Spohn steering linkage and ball joints
Moog poly end links
Eventually, I want to drop down to a 245/50-16 which is almost an inch shorter, then I can do the tall lower ball joints for another 1/2-3/4" drop. I may step up to the 5664 springs which are about 50lbs stiffer, as well. Pics on the first page of my build thread- click the link in my sig.