I had 550, 750, and 1000 cc KZ LTD's. Each had something in its favor. The 550 was agile, maneuverable, and the easiest to wheelie w/control. Mine I bought from one of the guys in the police dept. where I worked fire/rescue. He used to ride it to work, then it sat, and sat, and sat some-more, at the base of the PD broadcast tower. When the tires went flat, I offered him $200 for it and he took-it. I rode the bike as one of my multiple-bike stable, and sold it to my brother. It never required anything but normal maintenance, and never left me stranded (wish I could say that after owning a VMax for 20+ years!). It had a great cammy rush.
The 750, I was on a rescue call and saw the bike in a trailer park for elderly people, It looked out of place, as it was nearly-new. Off-duty, I went back to the residence and inquired about it. The husband and wife had co-signed for their grandson for it, a new leftover full-displacement bike from the time of the tariff bikes. For you young whippersnappers, if you're old-enough to have had to deal w/the concessions the Japanese bike industry made for Harley, possibly-purchasing one of the under-700 cc bikes, and being old-enough at the time to have legally-ridden one, you would be about 46 now.
The kid put a couple thousand miles on it, after having a new chrome Kerker 4/1 installed. He then wrecked it, scratching that voluptuous chrome Kerker megaphone with a fine random pattern of asphalt patina/grooving. He then lit-out, leaving his grandparents to pay for the bike. I showed-up at the right time, and got the bike with < 4K miles on it, for $800. It ran, the battery was drained, but the damage it suffered was cosmetic-a brake lever, the scratched Kerker, a grip. The bars I used an old downtube to bend back into shape. I ended up riding it for years, and painted the tank when the teardrop-design developed the corrosion where Kawasaki spot welded a bracket for their die-cast gas tank block-letter nameplate. I had 5 KZ's, and the ones with the screw-on gastank nameplate all got this.
The 750 LTD was roomier than the 550 LTD, almost as maneuverable, and also easy to control in wheelies. It was faster than the 550 as you would expect, and more-comfortable, with plenty of room for rider and a passenger. I rode it for several years and sold it for what I paid for it. ALso a reliable bike needing only normal maintenance. I did replace the front brake master cyl, as it was crash-damaged from the prior owner, and it looked bad. Hey, I didn't want someone thinking I did that!
The 1000 LTD I bought from another fire-rescue co-worker, and owned it a relatively short period of time , as an English guy offered me far-more than I paid for it. He immediately put it in an ISO container and shipped it (and about three dozen other bikes) to England for refurbishment and sales. By that time I was riding an FZR1000 about a year old, and that made the KZ's seem stone-age in performance, fit, and finish. I still have it, I don't ride it much, but it still gives me a thrill when I do. Yes, the ZX14 and the Hyabusa are about a second-quicker in the quarter, but I am not a drag racer, and this is paid-for, and when I tell people it's twenty-five years old they can't believe it.
I like KZ's, they were from a simpler time. They could take lots of hop-up, and my last one, a '82 1000J had 33 Smoothbores, GPZ1100 cams, an undercut Falicon tranny, a Kerker 4/1, Konis, and the nicest 'clocks' to stare-at while in the seat, my personal favorites of all my nearly four-dozen bikes I've owned. I sold it sight-unseen to a MN collector, and delivered it to his condo in Daytona Beach.
Try not to get too-carried-away with it, and the closer it is to stock appearance, the more attention you are gonna get. A Dyna S ignition, Dyna coils, better suspension front & rear, a halogen headlight, and good tires will keep it working better than stock, with better reliability, while still allowing a 'stock' appearance.