Hey there. It is coming close to the time when I will be needing new tires. I scored four matching Goodyear Wranglers with about 70% tread for $5 a tire. The tires I have on there now are P265/75R16. They are on aftermarket 16" rims. The Goodyear tires are P265/70R16. I've looked on the net to find out what the heck the 75 and 70 mean. It is the aspect ratio, that's what I understood from my search results anyway. But I still don't know if they will fit on my rim. Will the Goodyears fit on my rim? Enabling me to save myself some money? Thank you!

http://www.miata.net/garage/tirecalc.html will show you the difference in the 2 sizes. The 265/70-16s will fit but are an inch shorter in diameter.

//2000CAYukon

F.Y.I
I would never put a "P" (Passenger Car) rated tire on a 7000+# rig. If you do ANY towing and/or have it loaded with people, you are maxing out the weight rating on those tires. Load range "D" tires are what you are supposed to run for 1/2 ton (6 lug) and Load range "E" for 3/4 ton (8 lug). Those passanger tires will be spongy and less responsive due to maxing out the weight they were designed to withstand plus they will wear out FAST.
Also, more than likely your current P265's are load range "C" and the 70 series could be load range "B". Please check. (Which you should steer WAY away from with your heavy rig).
There are "70" series tires that are load rang "E" if that is the look you are going for, but never on a "P" rated tire.
Also, your speedometer will be off, but you can have your ECM reprogrammed to make it accurate.
Hope this helps. Best of luck