If you ever drive close enough to a modern car in front of you that if he panic stopped you would eat him up, change to discs. Original doesn't mean a whole lot if its totalled. That said, I'm doing the same change to my 70 Roadrunner and went with the stock Mopar brakes with the later disc mount for 11.75" rotors. I'm staying with 11" drums on the back and since these cars could be ordered this way in 1970 nothing looks out of place. I'm going for the right retro look with modern performance where possible.
Later, Jim