I was looking at some 4.30 gears (used). I believe that the # of teeth on the ring devided by the # of teeth on the pinion is how you get the 4.30 ratio?
Wow ... Ford does make a 4.30 - that's a steep gear! Your calculations were right on dividing the ring teeth by the pinion gear teeth. You gonna try to do wheelies? HA! I guess you will only need to use 2nd-5th! You're going to feel some incredible torque with those gears.
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'95 GT Laser Red Coupe - 5.0 w/T-5.
Extremely Ported and Gasket Matched Explorer Upper/Lower, FMS 65mm TB, Pro-M 80mm MAF, CAI, O/R H-Pipe, Flows Force II, MAC pulleys, FMS 9mm wires, Accel coil, sub-frames, MAC shifter, FMS 3.55's, '95 Cobra R's , SS Lines and Cobra headlights.
Well with the set-up I have the camshaft likes RPM's beyond 2000 while cruising. By the calculator on AFM with 4.30 gears at 60mph I'll see around 2300 RPM. I only travel 45min-1hr on the interstate with it maybe once a year and the rest of the time its a straight 55mph highway drive 30 miles a day round trip. No city driving except on occassion. BTW I am counting on it to be a huge difference from the 3.27's I have now.
To say the least ... you will notice a difference! Should be kinda fun! Like NoSlow said - do some work on that suspension!
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'95 GT Laser Red Coupe - 5.0 w/T-5.
Extremely Ported and Gasket Matched Explorer Upper/Lower, FMS 65mm TB, Pro-M 80mm MAF, CAI, O/R H-Pipe, Flows Force II, MAC pulleys, FMS 9mm wires, Accel coil, sub-frames, MAC shifter, FMS 3.55's, '95 Cobra R's , SS Lines and Cobra headlights.
ring gear & pinion? 
