Go to the link below and solve your rpm/gear/tiresize questions definitively. It's for trucks but it uses the standard ford transmissions. It's got fields for c4(auto), AOD, manual (4 spd) and 5 spd (t-5).
http://www.4x4cyberstore.com/website/rpmchart.html
On 15 inch tires with a stick, 4.30's is a bit much if you have any intention of streeting the car at all. I pull 3k at 75 and it feels like an awful lot. I couldnt IMAGINE running 3.3k at 60 mph!
Do this:
1. pick your maximum cruising rpm that you would want to maintain for hours at end
2. pick your average cruising speed that you find yourself drifting to
3. Match the 2 using the calculator and you have your gear ratio. I think you will end up with 3.73's
with 4.10's, a c4 and 225/60/15's you'll be doing 4150 at 75 and 3592 at 65 with a c4. Ouch...
I know the aod "sucks" but you might consider switching to an automatic with an OD (and beefing it up with a lentech, a hardened lockup shaft...etc) and then you can jump up almost 2 gear sizes and gain the acceleration through the first 3 gears and use your OD for cruising when you're driving it "like just a car". For comparison, the same setup with an aod only does 2800 at 75mph. Running at high rpms for a long period of time has strange side effects like the oil heating up and the oil pressure dropping and I dont even want to think about the transmission fluid temperatures. Just my thoughts....
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91 GT Carb conversion, holley 600 double pumper, edelbrock performer intake, FMS "C" drop springs, march 1000 underdrive pullies, crane 1.7 roller rockers, GT-40P headers, bassani x pipe, american thunder catback, FMS 4.56's, msd aL6, trunkmount battery, A/C eliminator kit, 3000 stall tci streetfighter, AOD with transgo kit, A+ servo, 300M hardened lockup shaft, kevlar bands and 28,000 gvw trans cooler, 3 core radiator, 300 lbs stripped with a full interior
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