I've got a Demon

Hey all, just checking in for the first time here and I look forward to working on the high mileage '72 Demon I just picked up. It's a 318 car with auto, PS and AC.
The first thing I'd like to do is find an easy ,cheap front disc brake conversion.
Anyway, this isn't my first Mopar, since back in the '70's I had '69 and '70 Super Bees and a '73 Barracuda.

This car was a gift from the original owner and he told me it got 23 mpg. Is this true for these cars?

Dan