I have been swapping motors since I was 16, that would be 40 years now. Snowmobile engine into XL250, 351W and 351C into Mavericks, 302 Ford into Mazda 808, all sorts of old sled configurations, even converted my family van to 4wd. I came into this with a lot of experience.
The welding is a big part of it. The chrome-moly frame needs special welding techniques or it will crack and break just outside the weld. The pipe is critical. Even my 50hp KTM motor will have less power than a Blaster motor if the pipe is built wrong. Chain alignment is critical so the swingarm cut out has to be perfect, can you really measure and fab that? And no rear brakes? Really guy, if you cannot fab rear brake or see the reason for them, you are not ready to do this.
I have seen many swaps attempted. Most never get finished. Wasted time, effort and money. Some get finished, but never really work right. More waste. Sell your 83 motor and put the effort into building a good Blaster motor. Cracks and holes can be welded or filled with JB Weld or bought on Ebay. Blasters are about the cheapest Rec Veh motor to rebuild and easiest to work on. You don't need a big bore or stroker to build 35hp (Raptor/Banshee hp) Buy a pipe and a rechambered head and ported cylinder and you can outrun a a Raptor or Banshee.
My KTM Blaster will do over 80mph (scary!) with the right gearing but then 1st gear is too tall. With 1st rear just right, top speed is 60mph and screaming. The gears are too narrow. My son's air-cooled Blaster (he has a DT200 liquid cooled Blaster as well) will easily do 65mph and first gear is still a rock-climber. The Blaster gearbox is perfect. In fact, with the exception of drag racing or hill climbing, his superior riding skills keep him ahead of me on the trail most of the time.
Yeah, we all want a special ride, but if it sits in the garage half finished or works like a turd, what is so special about it. Like an oversized motorcycle, you're just compensating for a small... self esteem.
Fix the Blaster and learn how to make it roar.
Steve