Mike,
Pro 5.0 is higher than the stock shifter and doesn't fit well in the ERA trans tunnel. In fact, I ruined one trans tunnel trying to get the Pro 5.0 shifter to fit properly
I had to order a new trans tunnel, and after speaking to Doug at ERA, just decided to use the stock shifter. I suppose you could make a spacer tall enough to make it work with the Pro 5.0, but it would probably look ridiculous. As it is, you have to use that 3/4" spacer with the stock shifter.
I am also using the GM Synchromesh fluid and haven't noticed and real problems shifting. I've got about 1300 miles on it now and the shifting seems to be improving with mileage.