a 59 1T would have come with a
5.14 stock, 4.56 was the 3/4T, the 1/2T could have had a 3.9, 3.7 or 3.38, if it does have a 3.7x ratio, it's not a 1T rear, but you have to know the ratio for that chart, it's not meant to figure out the ratio
I think your tach is off and you just don't have enough faith in how a 283 winds up, they love it .... you need to confirm the rear ratio [pull the cover and count the teeth or jack up one side and turn the up tire]
Bill
