Another Briggs Build: Help!

Picking up a Briggs-style (actually Kawasaki) flathead 4.5hp 160cc motor in a couple days. It fits std. briggs mounts, etc. I have a bunch of bike frames and spare mounting bits and brackets everywhere, but no welder and can only afford limited welding etc. services. Some important questions:

would a mount that clips on to the frame and is made of normal steel be strong enough? My prototype uses two 1/8 thick steel clips that clamp the frame using bolts and have a mounting plate in the middle. It works for larger frames and the gutted briggs I already have seemed to fit okay.

how to make a clutch? I will need to have a disconnect for obvious reasons.

how easy/hard is it to stick a cvt on one of these? how much for a cheap cvt?

dunno if it's chain or belt drive yet, would prefer belt-to-clutch and/or cvt and chain-to-drive-wheel but can compromise.

how to figure out gear ratios? don't want to spend ages building this thing only to realize it has a ridiculously low/high ratio. i am thinking a simple drive system of just motor-clutch-drive wheel.

and just to throw something out there: those cheap little LED flashlights make excellent headlights. rode on my (push)bike at night with two of them mounted motorcycle-style on the bars and was almost brighter than the cars that passed me.

thanks.

^I was thinking about that... prefer a manual clutch, but if it's expensive or a real PITA to make I'll get a centrifugal one... does ebay sell them? Heard they were popular in the karting world.

Thanks for the advice everyone- how would I get better valve springs? maybe the kart places sell them?

I already have some spare mini-airfilters and steel tubing lying around, freeflow should be easy.

Question about riding with a cent. clutch: when slowing down, do you just drop the throttle and then put on the brakes? From what I learned, the cent. clutch only engages at a certain rpm (like 1500) so when below that engagement rpm it acts like a disengaged manual clutch.