Check the adjusters - it sounds like they may need some fine tuning.
You didn't mention the fronts binding or how crusty or clean the assembly is but assuming it's clean:
You reassembled the rear cylinders with exactly the same type of parts that came out?
1: Ditto on the adjusters.
2: Pull a drum & see if you can push the piston in the rest of the way by pushing the shoes by hand or a clamp.
3: Sometimes the inner lining of the rubber hoses will swell enough to constrict the line, brakes work great with pedal pressure but won't fully release. This will cook your brakes, and more.
4: Possibly the friction points where the metal edge of the shoe frame rubs the back plate need a dab of lithium?
5: Were your springs stretched or did the coils snap tight when they were removed?
The first time I had #3 happen it was a real stumper. I recently read somewhere that a rubber line has a 6yr life although almost all I've owned were never changed.
On the DOT 5 fluid issue.
I'm doing some brake work on my Aero, got new rear cylinders installed and ordered a rebuild kit from NAPA this morning to freshen up an NOS master cylinder being installed. I asked about DOT 5 and they checked with the suppliers tech support who said to use DOT 4 with their kit.
