Ok, it's been driven on and off for the past 12 hours and all the problems are gone.
No noises at low RPMS in any gear, no more clicking, and no more vibrations. I still have mild transmission noise but I believe it's normal considering it's a franken-tranny I put together.
Oil Change monday and it should feel like a nice healthy car. Proper maintenance and care will pay off. 210K miles and counting.