Replaced the carburetor to manifold gasket yesterday and also changed the mounting bolts as I got the feeling they were a bit too short. It appears to have helped fix the 'missing' at idle. The engine now purrs like a kitten!

Still chasing the 2000 + vibration problem. I did some reading and it appears that there is a bushing in the C4 transmission extension housing that the driveshaft yoke rides in. Thinking back to when I changed the seal (which is still seeping by the way.) that there was some play in the shaft. I ordered a new bushing and seal today (12.00 or so including shipping.) and will change it out. Looks like I will have to pull the trans extension housing to get to it. Hopefully not that big of a deal.

We shall see.