Thanks for the replies, and also for the link to the previous post concerning the problem. The pulley was indeed stripped, and after I obtained a tool to remove the locknut, there was the next problem. With the pulley splines stripped, there was nothing apparent to hold the drive gear secure enough to break the nut loose. I read in the other posts about various ways to "put something in there" etc. to lock it up, or "jam the gears". I was a bit scared to do that, so, since I already had the top of the tranny off, when I inspected the gears, I went a bit further and removed the shift cam, and put the tranny in 2 different gears at the same time, by hand moving the shift forks, which locked up the tranny. Then, my impact wrench and new tool removed the nut with no problem.
An inspection of the main drive gear, and a good cleaning of the splines, shows it to be in good condition. I removed the oil seal and sprocket spacer where I could compare the splines where the pulley had been riding, to the inner portion of the splines, and they appear the same. I guess I'm lucky there, not needing to replace the main (5th) drive gear.
I think Harley has a sloppy fit there on those splines, whereas "normal" riding will rock the pulley to and fro, and over a short period of time (24,000 miles) it simply wore out the pulley splines. They are definitely softer than the gear, which is actually good.
I thought the problem may have been to little torque on the nut, since the lock plate is broken and spread appart, indicating that it had spun. It's never been off since new, so if that's the problem, the factory did it.
While I have it appart this far, I'm going to replace all the oil seals since I did have a drip leak from the tranny before. My problem now is pulling off the inner race from the main shaft to replace that oil seal between the main shaft and the inner part of the main drive gear.
There's another "special tool" needed, I'm going to make one to do the job.
Man, I just love to work on this thing!