Tire size vs. Gear ratio

From the tallest 15 that will fit in there,( about 28inches), to the shortest typical tire, (about 24.5), there is a 14% spread. Each successive gear swap between 2.76 and 3.55, is about 9%. So moving from 2.73s to 3.55s will increase your revs about 27%, and going from the small tire to the larger, will reduce the Rs about 14%. Adding 27 -14 = about 13 % increase in Rs overall.Here is the Formula;
(RPM x TC)/(1056 x R1 xR2) = Mph; where TC is tire circumference,R1 is rear gear, and R2 is tranny gear.

;with your 2.76s;and assuming a current tire size of 24.5 tall
So; (rpm x 77)/(1056 x 2.76 x 1.00) = 65mph,and rpm =2460(zero slip)

:with 3.55s and 28s(255/65-15)
So; (rpm x 88)/(1056 x 3.55 x1.00)=65mph.and rpm =2769(zero slip)

And to compare; 2769/2460 =plus 12.7%. Which compares pretty nicely to paragraph #1.

You didn't give your current tire size, so I assumed it to be a teensy 24.5 tall.Your results may therefore vary. The math is never wrong. It's just math.
A 24.5 tall tire, on a 14 rim,could be a 225/60, or a 205/65,or a 190/70, or a 180/75.