Clamp rear sprocket on 3-speed

I posted this in the intro section but thought I may get a better response here:

Hello, my name is Justin. I recently got the urge to build a motorized bike when I saw someone riding down the road on one. I did a little research, probably not enough, and then purchased an engine from berry bikes. I purchased the 66/80cc kit.

Shortly after a friend gave me a Columbia Tourist 3-speed in fairly good condition. The tires are in rough condition but they still hold air and the wheels are straight. There is some rust on the chrome and frame. The chrome is cleaning up pretty well with copper wool. If the build goes well I will tear it back down and have the frame repainted. I want to make sure I can get this thing up and running first.

I got the motor mounted tonight and shortly ran into my first bump in the road. As I said before this bike is a 3-speed, and the rear sprocket that came with the kit (clamp type) does not fit around the larger 3-speed hub. I was thinking of trying to find an entirely different rear wheel that has a smaller hub, single speed. I really dont care if the bike is 3-speed or not. Any suggested wheels I could replace it with? Does anyone have any suggestions to over come this obstacle?

Also I dont like the twist handle throttle that came with this kit. I'm going to have to cut the handle bar to get it to fit right and I dont like that at all. If all works well, I want this bike to look good. I really like the white grips that came with the bike as well. Are there other types of throttle set-ups out there and can I get them to work with this engine? I was thinking of a thumb throttle set up like a lot of atvs have.

Any suggestions or tips would be great

Disregard the throttle portion of my post, I've purchased a thumb throttle online. Hopefully it works out for me.

I'm not sure what to call my brakes. The bike has front and back hand brakes. There are no pedal brakes, the pedals free spin if u reverse. Even if I grind the center hole of the sprocket that came in the kit, the bolts will still hit the hub, and also the half moon plates that go on the inside are way too small for the 3 speed hub. I'm going to go to the bike shop tomorrow to see if they may have any suggestions on a single speed wheel, hub, and sprocket.

I really don't care if the bike shifts. I was honestly going to leave the shifter off. I just don't like how the twist throttle looks... I fell in love w/ the chrome bars and white grips when I first saw the bike. The twist throttle in the kit will not fit all the way on my bars and still be able to twist so I will have to cut my bars to get the twist throttle to work. Unless I'm missing something. Hopefully I can get the thumb throttle I purchased to work when it gets here. Im not worried so much about comfort, this will not be a long distance rider. I want the bike to be more appealing to the eye.

Purchaced a whole new wheel and sprocket today at a local bike shop. If all goes well, I'll buy a matching wheel for the front. Right now I'm having a little trouble keeping the clamp on sprocket centered while tightening. I'm getting a little wheel hop when I mount the wheel to the bike.