Just bought everything for 3.73 gears

I have the same gear ratio in my Barracuda, got carried away when I had RRP build me an
8 1/4 SG unit. After much soul searching I opted for a GearVendors overdrive unit and a custom built 79 904 based transmission with a custom non-wire lockup torque converter. I am seeing numbers in the 2400-2500 RPM @ 70 MPH range with the different calculators. Hope it works out as my plan for the car involves cross country driving and the Hot Rod power tour.
Good luck with your solution, mine was go back to 3:21.1 in a brand new rear end or pony up the treasure and deal with it.
DR--------:coffee2: