OK, so doing it the way typhoonZR said, in one full rotation of the tires (on the ground), the shaft spun 3 and about an inch which would in that theory be approx. 3:10 ratio, however, because both tires are on the ground and the car originally had 14's not 15 inch tires, wouldnt that put the rear gears at about 2:90? That would seem about correct, assuming that ratio was avail then.
So, if all this is true, and I go to 3:73's, this then will be a noticable difference off the line, True? And one more thing. If at 60mph Im tachin about 2400 rpms, what will rpm's go to at 60 with the new rear???

Phil...