[1G1YY]

I have a 69 12 bolt in my 62 with 3.08 gears and want to swap them to 3.73.
Local guy has 3.73 gears for sale with a carrier which is I think a 4 series unit, stamped 3866116. I need to know if I can install this carrier and gear set into my diff that is a 3 series one. Or am I better off using 3.42 gears that suit my original 3 series unit? Thanks, Pete