I used to run a Nash in my old car and replaced it with a Liberty when I started breaking it every other weekend. I was probably making 650-700 hp then in a car that weighed around 2500 lbs. There are some of those Nash trannys that didn't have a center bearing on the cluster and there was a torsional shaft for the cluster that was supposed to soften some of the impact. Back then I didn't have the clutch knowledge that I have now and I may have been easier on the tranny if I had a better clutch set up. If you're looking for a lot of good info on manual trannys and clutches you should check out
www.umtrdragrace.com . I think you will have to join to view the forums but there is a lot of info there.