Well, darn it, the agitator shafts are not interchangeable between a transmission that has a 4 bolt cover and one with an 8 bolt cover. Neither are the bottom shafts, not that it matters for my project.
The agitator shaft has a different O-ring arrangement, and the bottom shaft has a different retaining method, plastic clip vs bolt. Will have to go forward with the good used agitator shaft, instead of a brand new one. Plus the shaft retaining bolt broke, but it did come out, and I have a spare. Oh well, time to put the machine all back together with the good used parts. BTW, I used my neighbors new top load LG washer the other night, wonderful to let me use it, but, man am I glad I'm rebuilding mine. The clothes were never submerged in water, and barely agitated. Tiny detergent compartment too. AND, took twice as long. Progress, LOL.