so 2 things.
I agree with the others that smaller diameter will give you more braking force and you should probably pick up the manual master for the 70's corvette. it is the smallest GM one that I could find.

2nd, the pedal take up you describe does not sound right.
either you have some play in the front discs that you don't see, causing the pistons to push back, or there is something drawing the pistons back in.

but please explain how you know it is only the take up to get the piston to the disc?