Tire Sizing For A KZ550

Ok, I know the stock sizes are 3.25x19 & 3.75x18 on my KZ550. There are a few 3.25 fronts available, but I see no 3.75 rears out there. There are a couple of 4.00x18's available.
On metric sizing there are 100/90x19 (f) & 110/90x18 (r) combos out there.

Should I worry about these minor size differences? Will the 100/90 & 110/90 tires be taller than the stock 3.25 & 3.75 tires?
I see some Conti Classic Attack radials in 110/90x19 & 110/90x18 which look like some sweet aggressive modern tires for the old KZ550. I don't want to bog or slow handling too much with oversize tires...
Thanks for any insight.

On my 81 I'm running Kenda challengers front and rear. 100/90-19 front and 120/90-18 rear. The front is a tad tall as it comes real close height wise to the fender but works without touching. No issues with the rear. I have a couple thousand miles on the combo and see no issue with it.

I'm not specifically familiar with the 550 but typically a 100/90-19 front is fine if your desired tire type doesn't offer a 3.25.

For the rear a 110 or 4.00 should be fine. I believe the rear wheel is 2.15" wide which supports up to a 120. The only real concern is clearance for the larger tire.

Thanks gentlemen. I was afraid the 100/90 front might be tall compared to a stock 3.25.
I do have a set of the Classic Attack radials ordered as of this evening, tall or not.

100 90 19 for the front.
For the back I've gone back and forth between 120 90 18, and 130 80 19.

I get better hookup in straight line with the 130 80, but the 120 90 turns better. I'd probably recommend the 120 for general street riding. (Or even a 110 90).

Sorry about digging up an old thread, but I have a kz550ltd with the 16" rear wheel. Any advice on varying from stock tire size? I'm not opposed to getting a new rear wheel, but I'm not sure what I can fit in the swingarm. If anyone knows rear pivot spacing, or if any other models/years are direct swap, I can't find the specs anywhere.