Sometimes when you swap motors, transmissions or clutches you may notice that it gets more difficult to get into gear, or sometimes nearly impossible. In some rare cases you may need an extended slave rod. But usually you can fix the issue by simply adjusting the rod that attaches to the pedal assembly from the master cylinder.
It is a very simple process. Simply loosen the nut on that locks the rod in place (circled in red in the picture), then turn the rod clockwise to lengthen it. I usually turn it by 2 turns, then run the car to see if it needs more adjustment, and then do smaller adjustments until you get it just right.
Picture of the assembly so you know what I'm referring to:
