TLDR: keep s**t simple.
Don't mess with porting. A good china doll and basic bike maintenance is trouble enough before you break out the dental tools. A zeda 80 with a 44 tooth on a 26 inch wheel, fully broken in will be more than enough power. Especially because 22-25 mph on a bike is stupid fast. If you haven't gotten that fast through your own power you're missing out, big time.
With some relatively cheap parts you could easily save 5-8 pounds on your bike without sacrificing durability: take off some aluminum handle bars and aluminum wheels from a marketplace bike and that's a good 5-8 lbs right there. Not to mention the weight of the rims are felt about 13 times as much as weight of the hubs. With those horizontal drop outs you can ditch the derailleurs and shifters, that's another pound or so. Turn your 35 pound bike to a 25 pounded then add a 20-25 pound kit.
3 horse power on a 50 pound build is not bad. Loads of work on the bike side, even more to keep the whole thing running, but you can get something fun for not too much money.
The welds on your frame will be the most stressed part of any bike, motorized or not, so do keep an eye on them should you decide to put one of these turbulent little motors in there.