High Speed Rear End?

[EJFleming68]

I have a 1981 CC DS that I'm slowly upgrading as a part-time, as funds and parts are available project.

Since the original rear end in this cart is the old 16-spline female Terrill differential and motors are hard to come by, I found a 10-spline male differential to replace it with for $100.

What I've noticed is the existing setup is 2HP, 2,800 RPM and goes about 14mph with 18" tires. I worked out the differential gear ratio to be about 11:1.

The new axle is 6.25:1 and I plan up upgrading to 48V and solid state when I install it and doing lift kit and 21" tires

My questions are:
1.) Does this new axle have "high speed" gear set, is 6.25:1 common?
2.) Would 5HP, 3000 RPM motor (48V Solid State) get me decent performance? I've worked out that 3000RPM = ~30 MPH with 21" tires.
3.) I'm wondering if I need more torque but, I'm in FL and it's flat. Considering gear ratio and HP increase this should be about 40% more HP than existing setup.

Any feedback or guidance is appreciated.
Thanks