I don't know if there's a way to check with the stamped numbers. One way to check is to put the tranny in first gear mark the input shaft and output shaft at the 12 o'clock position count how many times you turn the input shaft to make the output shaft complete one full revolution. If the trans has the 3.08 first gear it will be over three if the trans has the 2.55 first gear it will be just over 2 1/2.