Well toycollector, according to your nick, your 30 year experience in the market, and the fact that you paid 5 grand for a K0, I'm assuming that a CB750 is a good investment.
My two cents about Vic World and restored bikes. It's true that restoring a bike without replacing any part, that is, chroming bolts and nuts etc, can be considered more praiseworthy than replacing those bolts and nuts. Or even replacing your blinkers for some of a donor bike makes the bike, at least to your eye, faulted because "those are not the blinkers the bike left the factory from".
I've never been inside a motorcycle factory, but I assume that there is a production line, and lots of people (if not robots) are assembling the parts. When they need a bolt to install an engine, the bolt didn't left the bolt factory with a sign saying "destined for CB750 with frame number XXXX". It's just a bolt among a box full of bolts. The worker picked up that bolt like he/she could have picked up any other one. What's the difference if you replace that bolt/mirror/blinker/handlebar for another one, who left the same factory -or was even produced in the same batch.
So, to my understanding, if Vic World or anybody else buy a bike and replace the parts for new ones, there is nothing wrong in that restoration. Imagine the worker of the assembly line picks up a lens, and suddenly feels an itch in the back. He leaves the lens, scratch his back -or crotch- and pick up another lens. Which lens was destined to be in the bike? Maybe the first lens left the factory in another bike and now Vic is reinstalling it where it was suppoused to be.
Even when a World's bike have a frame number and engine number combination that was never assembled in the factory, what's the difference? The reason for the difference between frame and engine number is probably that they picked up the first engine in the line without considering to match the frame number. So, for me, the engine is like any other part in the bike.
Just my 2 euro cents...
Raul