I understand it is very difficult to troubleshoot things remotely and I appreciate all of your help.
As far as the propeller shaft play is concerned, I have to admit I didn't actually measure it, it was more of a rough estimate on my part.
To me, it feels more than 3mm, but at the moment, I don't have a jack and stands handy to verify it.
Concerning the transaxle, I just finishied installing a new 300m output shaft, a new VCU (the old VCU was bad) and a new planetary gear assembly. There is 2mm of slop that comes from the new planetary gear assembly dowel pins sitting loosely in the new VCU, but I've come to the realization that I'm just going to have to live with this, because the new parts had the same amount of slop as my old parts.
Regarding the clutch, I installed a brand new clutch (centerforce DF) back in June. At this time, I checked the clutch splines/input shaft splines and they looked good and the clutch was a very tight fit. Since this time I haven't been able to really abuse my car, because I've been breaking in the new clutch and trying to track down the cause of this clunking. Personally, I can't see it being the clutch, as I had this problem when I was still running the OEM clutch.
As far as the gears are concerned, I took a quick peak at them when I had the center diff. apart and my _untrained_ eye could see nothing amiss. This definitely does not rule out worn gears, but with that being said, I've been led to believe that our synchros are the weakest point in our transaxle and you'd think they'd wear out before the gears would (mine are still in great shape)??
This leaves me with bad bearings and/or a bad center differential carrier, or do you guys have anything else to check or add to the list?
The thing that I can't figure out is, why does the clunk not occur if push down on the clutch while in decel and then slip the clutch back into gear (while giving it throttle) to accel.?
Thanks again.
Declan