General disc brake question

Thanks for the input, guys. It is a '68 'Cuda, soon to have a 440 & 5 speed. I want it for street use, so it will not see a 1/4 mile or road course track, but I want it to stop like a newer car. I noticed that the aftermarket multiple piston brakes are much more expensive than single piston brakes.

How about rotor size for this application? Is bigger better for the street?