psguy, I don't think it has a meaning outside the factory. The 8 looks cast in, then the other for digits are stamped in. I have one head here from an 82 engine. The number on the rear of the head is like that but on the front and verticle, it's 8 R26.
The numbers stamped into the head and rocker cover, and the number on the upper and lower cases are just for matching the parts.
They are cast then assembled together for the machining. Once machined they stamp the numbers to keep the matched parts together.
nelson20vt, your parts bike looks to be an 82 or later. Those lower side covers are kinda rare. Only fit the later models, won't fit the 79 frame. The seat, grab rail, and side covers won't fit either.
Most every ting else will.
If the 79 had the disc brake on the rear, just put eveything from the brake pedal back from the parts bike on the 79, swingarm and all.
The rear fender might be different, not sure on that. Side stand i think is different.
The 79 used BS38 carbs, the parts bike has BS34's. THe stock air boxes of the parts bike may or may not fit the 79 frame.
Engine, front end complete, wheels, center stand, tank, shocks fit.
On the wiring, unless you want to keep it stock, simplify it. Build your own, leave out all the unnessasary crap.
Leo