I did a similar swap on my desoto 318/833. I used a 3/4” master and a speedway motors 3/4” push slave. I was not able to get enough travel no matter what I did. I tried moving the slave mounting point further in on the clutch fork, but it still was not enough. I did drive the car for a while but knew the grinding was not good. I put an hydraulic throw out bearing(not the kit,just the bearing)in it and it worked much better. I welded a piece of sheet metal on the backside of the firewall for reinforcement and drilled/cut the holes for the master, after making a template of course.