Long Dormant Deere 820/2010 track loader – tracks locked up solid

As I peel away and correct problems with our newly acquired 1963 John Deere 820/2010 track loader with backhoe attachment, I'm now down to a major one in that the machine will not move freely and both tracks appear to be locked up solid. My first thought was that the steering/brake bands may be seized onto the drums after unknown years of sitting outdoors without running. After getting the beast up and running with new filters and fluids when I have the gear selector in "Tow" it is locked up. We had to winch it up onto the tow bed with both tracks locked. I checked to ensure that the brake pedal lock was not engaged and the there was some travel to the brake pedal. Both steering levers appear to be in proper position and seem to operate with travel as normal. AS found. the right side rock guard over the rear drive sprocket was off, and the seat assembly was also removed, both parts sitting in the bucket when we bought it. After getting the tractor started and running strong I tried putting it into the lowest gear and engaged the clutch and reversing lever back and forth to see if I could power it out of the seized condition. No dice. It seems to me that with the differential and one track problem, the other track would run in reverse direction, thus my thinking that the problem is more likely to be with the steering/brake bands and drums. With a large excavator and a 1956 Cat D4 7U dozer that have both had extensive work needed over the years behind me, this is the first time I'm dealing with a final drive problem like this, so am looking for any guidance that might make the diagnosis and fix easier. Many thanks, -Tom