Join Date: Sep 1998
Location: Colo Spgs, CO, USA
You could go with the disk/disk master cylinder, but you need to things: an adjustable prop valve in the rear line, and also a 2 lb residual pressure valve in the rear line. This will allow you to fine tune the brakes with the adjust valve, and keep the pressure in the line like fig said.
As far as noticing a difference, that depends on a bunch of things. First, why would you think you need the larger front brakes or the rear disks? For a cruising car, they are not necessary and you will not notice any difference. Not until you get into some pretty aggresive cornering and repeated stopping will you see any difference. Then, it also depends on how the car is set up. One thing about rear disks is that you can lock them up pretty easily, so in a normal car, you will have to adjust the bias down to a point where they don't provide any additional stopping power. If you have tightened the suspension and are keeping weight transfer during braking minimized, you can get more bias in the rear brakes and then you will notice a difference.
I have done quite a bit of work on rear disks for my Chevelle, so I can offer additional info if you want, but they simply are not a simple bolt on and go type solution. Plus, the rear calipers tend to be a PITA.
One option you might consider for some additional rear braking power is to use some 11" rear drum off a 76 or 77 Monte instead of the 9 1/2" stock ones. This lets you keep all your existing disk/drum hardware like MC, prop valve, lines, etc. and get better braking for cheap! A lot less than rear disks!
Colorado Springs, CO
68 Camaro... someday!
71 Chevelle SS