snoman

You simply get a ring and pinion and new LSD unit based on the rear
axle you have, not tha year truck it is because the axle type is what
matters here. You either have a Sterling 10.25 or a D70. A 4.30 was a
ratio availble in ford rear axles in 250 and 350 trucks and is a great
towing gear and you should consider that instead of a 4.10. Also stay
away from a dealer for these axle parts unless you want to get skinned
on price. Below is a link to a GM axle ID pics (sorry about that but
it has a D70 on it and I have not put one together for Ford yet) that
may help you ID your rear axle.

http://forum.snoman.com/viewtopic.php?t=188
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The SnoMan
www.thesnoman.com