Still not sure what to think. Maybe i can attach the tach meter in such a way that I can get some idea of what RPM it is running.

If the memories are correct and it used to go a lot faster, the only thing I can think of is that the clutch is slipping. I may have to go test that theory as well. I was reading about how oil can get on the clutch plate and the thing certainly has been leaking a bit

1953 Chevy 3100
In the Stovebolt Gallery
My truck pictures