I have resently done some wheelin and dealin and inded up with a 3 speed manual and don't know what kind it isand needed some help. It has 7 bolts on the side sifter cover no groves in the input shaft but has someware close to a 3.11 first gear and has 5 bolts to bolt it to the bell housing (the standered 4 +1 top dead center) all I know is the guy said it was a heavy duty 3 speed.
i run a m20 or m21 with a big block never have hurt it one bit its up to you !!!! also had one in our race car 30 years ago 67 camaro 327 .60 over 12 and a half to one compression two 660 holley center squirters on a tunnel ram flat tappet norris cam shaft ,1957 olds rear end with 5;57 gears summers brothers four bolt mains, slicks !!!! no n.o.s on gas 11.02 et 124 mph !!!!! never ever hurt the m20 0r m21 muncie !!!!!!
Sounds like you have a Saginaw truck 3-speed. IIRC, the Muncies have a 9 bolt side cover. There is nothing wrong with it for daily use, other than lacking the gear spread of a 4-speed. Most of the IMCA dirt Mods, and Hobbys, around here still run the Saginaw, if they can afford a Bren. Personally I like the SM420s I have in my 49 & 62. They shift smooth, and take abuse well.
