[Synchro909]

This thread is moving off the original topic but here's my experience with the short pitman arm.
My Brother In Law recently bought his first Model A. It had been fitted with a shortened pitman arm and because he bought it quite a distance from home with lots of twisting, turning mountain roads to get it there, he asked me to drive it home for him. It was terrible. There was waaay too much play at the edge of the steering wheel and the car was not easy to control into and out of a corner. When we got it home, we did a few things like readjust the way too tight wheel bearings, adjust the brakes and while we were at it, we put the original arm back on. When I drove it afterwards, it was a whole different car. Steering was back to normal and it was a pleasure to drive. I'll never fit one of those on any of my cars. It is blindingly obvious that whatever free play you have in the steering with the standard arm, you will have more with a shortened one.As for the OP's problem getting the arm on the sector shaft, I'd be reluctant to file anything. I'd try again with the slot held open as far as needed and making sure the arm is aligned with the shaft properly. Don't expect for it to slide on easily. you should have to "encourage" it with (not too hard) blows with a hammer.