bigger rear disc in rear than front a problem I assume?

Not sure, but keep hearing people having problems with 15" wheels and the 12.19" kits, and I don't know anyone that has a wilwood setup I can test it on. I really want to keep the wheels, I'll even buy some aftermarket 15x10s cop style wheels if I do minitub the car.

Have you asked @HemiDenny? I'm sure he has an idea of what some of his customers are running for brakes and wheels.

The other thing is, I don't think the Wilwood hubs will clear the factory cop wheels to begin with, regardless of the rotor size. The hubs used with the Mopar Wilwood kit definitely won't, the hub diameter is significantly larger than the hub bore on the cop wheels. Not sure about the MII kit. Do you have the part # for the Wilwood kits that you want to use?