The U-shaped shift collar at the rear straddles the low-reverse sliding gear. The front shifter with the narrow slot engages the raised ring on the 2-3 synchronizer. With the transmission in neutral and the shifter lockout on the side cover in the middle position, it should be very obvious where those parts fit, unless your name is Stevie Wonder or Ray Charles! The forward shifter with the narrow slot is notorious for getting worn, so be sure the slot isn't V-shaped.
Jerry