Help for disc brake upgrade on second gen

[slickrig]

I would like to upgrade the calipers to 4 or even 6 piston on my 79 Z28 but don't want to change out the stock 5 spoke rims and tires I did alot of work seting up the tires and wheels and I'm happy with the look and performance of the current set up. Front brakes are stock and changed out the rear end for a factory 10 bolt posi from a T/A so now it's disc disc.
Any sugestions