It was mentioned that it won't free wheel. I have one tractor that has a very sensitive and grabby fwd-rev clutch and to move it I have to make sure the handle is in perfect neutral. Make sure the range selector (Swiftamatic) is in high as well.
I would not be anxious to remove the engine or disassemble anything until I got it running and was able to assess the overall condition of the engine and transmission. O certainly would not disassemble it on that table.
If the engine doesn't smoke or knock, the transmission works and is not noisy then I would leave it alone. The 5665 with the snow blade that I restored didn't need an engine overhaul or any transmission work. It's faults were mostly cosmetic with the exception of rusted out engine covers, loose magnets on the flywheel, bad fuel line. It had a bad condenser which prevented it from running.
The 2nd 5665 needed an engine overhaul and transmission repairs as it had been used, abused, and neglected for 3000 hours.
One tip when rebuilding 50" mower deck spindles. Have a capable helper. It will make things go a LOT faster. My son and I worked in tandem in a 50" deck and it took under an hour to R&R and rebuild the spindles. He worked outside removing and installing the spindles and I worked inside disassembling the spindles, installing new bearings and reassembling. He would bring one spindle in, take the completed one out, install it with new fasteners and take the next one out. Just about the time I completed a spindle, he would bring in another. One day I will write up a little blurb on rebuilding deck spindles. There are a few points that are a little different about them.