As stated previously, manual disks can work fine, and are frequently used in racing. I prefer them myself. The trick lies in getting the bore sizes correct.
Do some research and find out exactly what model brake calipers you have. You'll need to know when it comes time to replace the pads anyway. Most likely GM metric mid-size calipers, aka 78-87 A-body, Malibu, Monte Carlo, Grand National, etc. Check the bore diameter of the caliper, then look back in the past when cars were available without power disks, late 60's and early 70s. Find another vehicle with that diameter calipers and find out what the bore size is of the corresponding master cylinder. Then you can use any master cylinder with that bore size that will bolt up.
Your pedal should already be set for manual brakes if it is original.
Devin
