Ordered a gear vendor, help with deciding gears

Figure out where peak torque is on your car (I.e. dyno).

Figure out how fast you want to run on the freeway.

Pick the deepest rear gear as close as you can to make the two above coincide in top gear. You'll need your tire size and calculators for this are all over the net.

It really is that simple.

Maybe someone else covered it, I ain't reading all these posts.

Example. Peak torque 2500 RPM.
Freeway speed 80mph (you's in Montana an alla that).

From their website:
Overdrive is 0.78.
So by the chart, the gear in red will behave like the gear in black.
Dodge 3-Speed Auto - Gearvendors

So with this calculator, 3.23 is your bingo (I just picked a tire size, Your mileage will, literally, vary)
Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio

Switch to 3.55's, and you're cruising at 2800.

Compare this to a true six speed with double-over, and you'll see why people don't like the GV unit.