1980 Kz440B tire questions

Howdy folks. I recently acquired an '80 Kz440B as my first bike. The tires on it LOOK great, almost new, cosmetically, but the were manufactured in April 2000. I just don't feel good about riding around on 2 wheels with 20 year old rubber, regardless of good the tire looks.

So the spec sheet has the front listed as a 3.00-18, and the rear as a 3.50-18. Tube tires, as the wheels on the 440B are spoked wheels. Found a set of IRC GS-11 in those sizes online. I go to double check the stem location on my wheels, and notice that the current size tires installed are:

Front 100/90-18 (3.25/3.50-18) TUBELESS
Rear 110/90-18 (3.75-4.00-18) TUBELESS


Now I'm a bit bumfuzzled. First, the current tires are larger than the spec sheet has listed. Is that normal, or acceptable?

Second, is there any way to figure out if my wheels have been sealed to run tubeless tires, or did they just install tubes inside a tubeless tire?

I was really hoping to get a new set and installed by Friday evening, so I could do some riding this holiday weekend.

Thanks!