248, good info,I believe the first first T-10 design were 2.20 and 2.54 ratios in GM cars and 2.36 in Fomocos. My experience with Saginaws behind 300 hp or less and not drag raced with slicks was they hold up ok.The front bearing wear is a mantenance problem when driven hard.As a young man I had no problem tearing the cluster teeth off a Muncie in my 327-300 Impala,and later twisted a main shaft in a reasonably stock 396-375 Chevelle with tires.I was really brutal,blew 7 trannys in as many months in my first car,a 56 Fomoco.One time busted the tranny, tore off the clutch disc facing and the rear end spider gears all at the same time.
So maybe I'm not the best guy to get tranny info from
Four, all the Muncie's I ever saw were aluminum.M-21 etc is an option code, Saginaws 4spds also carried those numbers.
