ok cjren,
what you are trying to build isnt for the faint harded, you have to decide wether you want chain drive, belt drive etc then you have to work out sproket sizes etc, i like to build as well but i have stuck with the kits readily available from the various vendors.
The way i see it i could try and do some homemade tinkering, but my metalworking skills are little if next to nothing, welding etc, out of my league, most of the guys who do homemade kits build amazing rigs and one thing they have in common, they have decent fabricating, welding, metalworking skills,
If you want to build without blowing the bank try a happytime kit similar to the build you just visited, i was going to post a link to the electric/ht chopper,
You should have no problem working with this engine, the problems you will have is engine fit on that trike you looked at.
Ok so i think your happy with the happy time (2 stroke engine) hundreds of builds here and a ton of advise if you need it, check out thats dax website and you will find a excellent step by step walk threw of how to install the kit, U Tube is full of builds as well,
The biggest problem is trying to find a trike to put it on, yes a conversion trike kit could work for you, but bike size will be a factor, if you check out the rolling pics on the banner you will see a 26inch three wheeler with happy time installed.