Truth is they all can be a PIA. 4 piston calipers, sliders, drums all have their hangups. Drums are just a bit more complicated and I agree, changing pads is usually a lot easier than changing shoes.
You should not have to do much adjusting on the drum brakes if everything is working right. The self adjusters should do most of it. So while you're looking into front calipers, you might see what can be done to improve the drum self adjusting. It will still apply to the rear brakes even when you do switch. The rear brakes are most important early, before weight shifts forward. So they effect initial feel and response more than many people realize.
This is a pretty good pamphlet for the '69 up style shoes and adjusters.
Drum Brake Service Highlights (Session 260) from the Master Technician's Service Conference
The ref to early adusters in the above pamphlet still refers to the '69 up system. TSB for the change is here:
The 1970 Hamtramck Registry "1969 DODGE MODEL TSBs Index" Page
This booklet covers the Kelsey Hayes 4 piston (fixed caliper) system used on A-bodies through 1972. I think it provides a pretty good overview which is useful even if you don't go with the factory system.
1967 Imperial & Chrysler Disc Brake System - Session 233
