e-150 ring and pinion

I have a 1994 e-150 econoline with a 5.0 v-8 engine and automatic transmission. I need to replace my ring and pinion gears but do not know what ratio they are. The plate on the rear end housing is missing. The only information I have is that the axle code is 17. I searched the internet and found that code 17 means 3.31 ratio gears. These are expensive and hard to find. Could I install 3.55 ratio Ford Racing gears and replace the speedo gear to match the new ratio gears? I had my ring and pinion gears changed on my 1988 Mustang GT. I upgraded to 4.10 ratio gears and replaced the corresponding speedo gear to keep the speedometer working correctly. Could I do the same with my van?

I would opt for either 3.27 or 3.55 gears, but yes you can simply change ratios.

As I recall, by '94 all Ford trucks and vans used a speed sensor in the rear end on the differential housing, and not one in the transmission. If you have a VSS in the diff, there is no need to do anything.

What is a VSS? What does it do? How will I be able to tell if I have one or not? Information greatly appreciated. Thanks!

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