3.73 or 3.42 with 33" tires

[Mike C]

In the early 70's they chose gear for good all around performance not just for mileage. And the 3.07 gears with 28" tall tire is what GM thought was best for the 350 powered 1/2 tons.

33-28=5. 5/28=.17857 So the 33" tire is 17.86% taller than the 28.
3.07x17.86=.5483 and 3.07+.5483=3.62 So 3.62 is 17% more gear than 3.07

So to duplicate what GM thought was a good all around gear ratio you would want to go with a 3.62 gear. Since that is not a choice, you can go a little bit more gear with 3.73 or a little bit less with 3.42. With an auto and converter slippage along with 75 mph speed limits common, I would run the 3.42