yeah, and probably an electronic to mechanical speedometer adapter to.
I chose to use one of these in my 1940 gmc project because I was swaping out my 4 speed crash box and torque tube and needed to use my factory bellhousing for the clutch and brake pedal mounts. I am also running 4.11 gears which turn into a 3.00 in overdrive. I think the best you could get with a Gear Venders unit is a .8 overdrive, or a 1.25 underdrive.
With 3.90 gears, the gear vender final drive will be 3.12. With the NV4500 it will be 2.85. That would translate out to about 220 rpm difference at 65 mph
