I have upgraded the brake system on my 70 Charger RT. My car came factory equipped as a power drum brake car.
Here are the changes that I have made.

Front Brakes: 11.75 in Mopar disc conversion
Rear Brakes: TSM kit (11 in disc with GM caliper)
Master Cylinder & Booster: New for a disc brake 70 Charger.
I am still using the original distribution block that came on my car.

What changes do you think need to be made if any. I have yet to get this car on the road as I am coming to the end of my build up on it for this summer.

15" wheels if you don't have them already. I would also add an adjustable proportioning valve in the rear brake line behind the distribution block.

You may need a proportion valve. You need to make sure the car does not spin easily due to too much rear brake grip in relation to the front brakes. Try some panic stops in the wet. If the back brakes lock too soon add the valve into the brake line going to the rear brakes. Make sure you also simulate a panic stop while cornering in a large wet empty parking lot.

http://www.mpbrakes.com/products/product-detail.cfm?product_id=612

maybe a set of semi metallic pads for the front. I just got a set & they gotta be better than the organic pads on there now.