Well, dang it. I'm not going to make it out this year after all. It seems my car is not co-operating right now. There are some funky noises coming out of the drive train, and I won't risk breaking down far from home (if I can avoid it). Ahg.
I thought it might be a u-joint, but changing back to the stock driveshaft did not solve the problem. Now I 'm pretty sure it's something in the rear axle. I will try to get another (professional) opinion on my pinion today.
So count me as a maybe, but more likely as a probably not...