A '56 3 speed won't have a syncro first gear. That wasn't adopted until the mid '60 (66?). Most likely it's an SM318, which uses a slider gear for first and reverse. A way to tell if it's a '55-early'56 or late '56-up is by the shifter cover, the 55- early '56 use a seal that looks like a small axle seal, the late '56-up uses O-rings.
