1973 340, want more power.

If your not going this be on the Hwy. much, 3.91's are fine and with the tall tire, not to bad of a combo.

The "Good compromise" gear choices are 3.23 & 3.55. Normally MoPar's do not come with 3.73's. But those are the 3 ratios considered to fall into that category. And tire size (height) has a play in that as well.

I have run 4.10's for decades. I last had 255/60/15's out back and IMO, it was excellent for the build, car & performance intended. I had no issue being on the Hwy. Of course, I did not travel very fast. 60/65 mph was the cruise speed. The car was a manual and the tack ran around the 3300 area. I do not under any way consider that spinning the engine high for Hwy. driving for the build that it was and the set up it ran. A lot of people cry like they have a baby at that.

If that's to much for you.......