Jeff, Ya, that does sound like low "R,s " for a 373 gear and I say that cause I've got a car with a 3.36 gear,15in. tires and it turns 3500 RPM at 70 mph, so a 3.73 should be turning even faster unless you have some tall tires on the rear.
Ya better check the ratio on that rear again.
No dis-credit intended but to hear you asks how much work is involved with a gear swap says maybe you ought to have it done.
I've been a wrench for 40 years and even though I could do the mechanical part of changing the gears I lack the neat tools which make setting up the gear easy. Backlash and tooth contact pattern have to be right or the gear may howl.
Randy's Ring and Pinion in Everett, Wa. has about everything you might ever want for your rear-end.
He can tell you, given the tire size you need to run ,what ratio will be needed to turn what ever RPM you would like to be at when doing 70 MPH or whatever speed.
Dan

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