Some things will interchange, some won't. The master cylinder will bolt on, but the bore sizes are probably different since the C20 used bigger brakes. The booster should be the same either way. A reman master cylinder can be had for about $25 if you do some looking.
The 400 should go right in, same for same.
Go for the big block. The torque makes such a difference. Since you have a parts truck, just pull off everything you need. The BB springs will go right in.
What will not interchange however is the front brakes. If you want the big drums of the C20, you'll have to change out the whole spindle assemblies. Not a big deal, since you'll likely be changing the springs anyway, it's just a matter of disconnecting the upper ball joint when you take it apart. May have to change the ball joints, too come to think of it.
Devin
