Rear gears

[Longhorn Man]

a 350/TH350 should already have the 4.10 gears (assuming still stock) and as said, that's about the best you'll get. There used to be an aftermarket gear, I think it was a 3.90, but it's safe to say you'll never find one.
The RPMs do seem high, and while Tim is right, you can just live with it, and they were in fact built to run on the freeway @ 70MPH... however, it does wear the engines faster, and does consume more fuel on most vehicles.
I would recomend either adding an overdrive trans, or swapping to a later rear end with more reasonable gearing. The reality is, putting a 3.73 gear rear end will drop the RPMs quite a bit and you can still haul/drag anything you want. If you have the truck grossed out or overloaded more often than not, then you should probably keep the gearing, but if running empty/lightly loaded, then I would recomend an upgrade. My daily driver C/30 has the same gearing, and I am swapping the rear end for a 14 bolt with 3.73 gears, with any luck, it'll be in there this summer.