chevll - I recently switched the rear in my 54 from the original 3.90 to 3.55. (3 speed tran) i have not been able to drive it very far becasue i have some brake issues to deal with but Frank50 makes a good point. you will not see a tremendous amount of difference in anything by going from 3.9 to 3.55. i was fortunate that i was able to purchase a rear that already had everything rebuilt in it with the 3.55 pinion and for a very reasonable price. basically all i had to do was slide one out and slide one in. it all depends on what you want to do with your truck. if you are out there cruising and in fast traffic all the time then, in my opinion, you are much better off ditching the torque tube and spending your money on the blazer or s10 set ups that everyone is using. If you want a little driver to mess around town in and for short trips in no hurry then the torque tube is just fine.
