Sounds like you have the 4.11 gear, what is causing the main problem with the speedometer/lack of speed issue are the tires. 235/60/15 are much smaller in diameter than the oem tire (26" vs 29"). That will cause the speedo to read off, plus limit the top end, as the shorter tire will be the same as if you put a lower gear ratio in the differential. To improve the speed issue, there is a 3.55 gearset available from Patrick's, or you could go with a taller tire.
