I switched to 3.55 last fall and then installed the 200R4 overdrive transmission in the winter.
We ran down to Yellowstone and back (2000 miles) and I'm really happy with the results.
Speedo's not working and haven't checked with GPS yet, but I'm down from about 3300 rpm at 70 mph to about 2600 rpm. The nice thing is you still have the good launch ratio (actually, slightly better in 1st than the TH350)
