And, there's this...the bike has the Black Molly Paint...but it does not have the "Turbo TC" lettering...and...it does not and never has had...a Turbo!! Any thoughts of what I've got?
You should post some pictures. It's fantastic that you've owned it since new. Some period pictures would be especially fun.
Based on the numbers, you have a 1978 KZ1000-D1 Z1R, which is what you thought it was. My own research indicates that the highest frame serial numbers imported into the US was around 8000 to 9000. So you have a later US production bike. I'm guessing your head tube is stamped with a manufacture date of 11/77?
From what I've read, the '78 Z1R did not sell very well, and there were a lot of bikes left over after 1978. That's part of the reason that a bunch of them were sent off to ATP and modified with Turbo kits and then resold as the Z1R-TC. They had plenty of dealer stock that they were happy to move.
My guess is that some sales manager, who had a 1978 model still sitting on the floor in 1980, had the clever idea of having the bike repainted in the TC Molly colors as a way to dress it up. Plus, the 1980 model was black so maybe repainting it would cause some folks would mistake it for the 1980, so wouldn't notice that it was a 2 year old model. Just a guess.
Also, most sources say there were 500 Z1R-TC bikes converted, and that the first half retained the stardust silver paint, while the second half got the black molly paint. It's always possible that the dealer actually did sell a Z1R-TC at some point, but the buyer asked to swap the black molly painted parts with the stardust silver parts. Always possible, especially if the two bikes were sitting next to each other on the floor.
