Depends on your combo. I've got an SM420 Muncie 4 speed with a supergranny first with around a 7:1 ratio. Final drive is a 1:1. I have an SM465 Muncie 4 speed, also with a supergranny first, that will readily adapt to a transfer case for 4WD that I'd really like to use.
Although I'd really like to get a 3.50 differential ratio, (Dana 60), a 3.73 WOULD work too. 3.73 x 7.0 = 26:1 ratio. You can jog faster than top speed in first gear. And 75 mph would be around 3100 rpm with my tires. 3.50 is a little more useful, with 2900 rpm at 75 mph. But either would work with me.
Your combo depends on what you've got, but for most combos, yes, 3.73 would work well.
