Hi echotraveler,
The front brake has always been a drum type. The rear can either be a "coaster", a "band", or a "drum" brake. If the bike was the manual clutch version the rear brake was the "coaster" type. If the bike used the automatic clutch the rear brake was the "band" version. In the later production motorbikes the rear brake was upgraded to the "drum" stlye. The "band" brake with a little effort could be upgraded to the better drum system, and still use the same rear wheel assembly. The original "band" brake hub could be removed and repaced with the heavier hub [threaded] and the brake "pork chop" and heavier cable would produce a better rear brake.
Consider the following...........
The coaster brake hub used "pressed" on spoke flanges, and were subject to failure on many fronts. Most often the flanges simply pulled loose from the hub, on several of my personal bikes the inside finish of the hub was very crude and "locked up", destroying the bearings and bent the axle. All failures were due to quality control and design, not speed and or weight as often portrayed, in fact the vast majority of the problems I personally incountered were on 100% stock motobike with an average weight rider [160 to 225 pound].
The band brakes were never impressive, and I have replaced several that the material seperated from the metal band. I even tried several where the stopping material was "glued" on the band , only to witness the material breaking off in "chunks".
Having said all that, the upgraded rear drum brake system is by far the best solution. If you have the automatic clutch version, then simply purchase the much better rear drum brake system.
If your bike has the "coaster" rear brake then either replace with a "vintage" Bendix, New Departure, or Morrow hub, or use a modern day Shimato, Worksman, or any with a one piece hub [do not use any hub where the spoke flanges are pressed on].
None of these comments are intended to "bash" any person, persons, company, or vendor, just to help with safety of fellow riders.
Have fun,