I was hoping to use a belt drive from the motor reduction to the rear wheel.... but it is pretty much a custom piece and pretty pricey and the source for this piece has been a bit difficult to communicate with.
So for a number of reasons... primarily price and easy availability I've decided on a little different route. Instead of a one way bearing and belt drive... I'll be using a BMX freewheel in reverse mode... driving instead of driven... and a crank chain wheel on the rear wheel. It is is going to require a new rear wheel with a mountain bike type hub with provision for a disc brake rotor mount.
I created a spread sheet to analyze the gear ratios needed to end up with a target speed of about 30 mph. My home built trike has a 24 inch rear wheel so it requires a little more reduction in the drive train than would a 20 inch rear wheel. Still debating somewhat..... whether to use an existing motor that I have.... or bite the bullet and go for one of the Astro motors.
Some parts will be the same either way but going to try to keep it as simple as possible. A 44 tooth chain wheel on the rear wheel.... bored and drilled to fit the brake rotor mounting holes. A 13 tooth BMX freewheel driving that. It will require a a custom piece to mount on to a 16 mm jack shaft. On the other end of that shaft will be a 5mm HTD belt drive pulley and a smaller pulley on the motor to complete the drive train.