true rear end ratio?
 

Curious as to the correct rearend ratio if tire size actually reduces the productivity of the gear itself. 245 to 265 they are 1 inch difference in diameter obviously.......... which is actually the size they were designed to retain the gear you had wanted? 245 tire changed to a 265 or vice versa loses/gains roughly .13 of the ratio.

Try this site. pretty handy for just about everything

http://www.csgnetwork.com/automotiveconverters.html