3.91 gears w/ 3.23 speedo

Tony with 3.91 gears and your 26" tal tires (275-50-15s right ?) you'll be spinning 3278 rpms at 65 mph, 3795 rpms at 75 mph and 4298 at 85 mph.

http://www.quiknet.com/~ke6vut/rpmcalc.html

Your motor should be broken in enough to change to synthetic oil.