So I finally get me speedcal in the mail, install it, program the code for 2.73's swapped to 4.10s with 245/45/17 tires. And go for a ride. Now the speedo is too slow instead of fast. I try a different code, no luck, its still 5 mph off at low speeds and up to 30 mph off at higher speeds. So I try a code for 3.27's just to see if it does anything, and it brings the speedo closer to where it needs to be but still no cigar. I get pissed and sit here trying to figure out wtf is going on. Then it dawns on me, I should decode my door tag, and low and behold, I discover the code of "E" on the axle portion of it. Now, does anyone know what E stands for? Yes you guessed it, the optional 3.27 gears with the trakloc diff. No wonder the 4.10s didn't feel that much faster and now my 15.02 1/4 mile time makes sense. I guess this is a good thing, b/c now I think i'll keep those gears as a back up, + I can get more than $20 for them. So after driving the car for 2 years, I finally learned what ratio I had. For some reason the stock diff cover had 273 on it. Guess it was a ford screw up. I guess I could say that "It all makes sense now" I was wondering why it was so easy to boil my tires off the line and why so many people were saying it was faster than they though it would be.