Muncie SM318 was the model number used in TF trucks and through the 60's. I have seen the early transmissions referred to using that model number on this site. They are completely different but may still use that designator. If you need to order parts, it's better to refer to it by the year.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine