3.50 or 3.55s

[Hammer500]

my uncle is a mechanic and has a 72 cheyenne super with a 402. He played around with all different gear ratios and said he found a set of 3.50s or 3.55s in what he thinks (from his memory) was a 73 or 74 truck with a 12 bolt. He says that is what is still in his truck and worked the best for him as far as driving on the highway and at the track. Has anyone ever seen a gear ratio in a 12 bolt truck that is in the 3.50-3.55 ratio? If you did what was it in year, engine, tranny?