Yes, leave the arm on, imho. A pickle fork would be handy.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I followed that tutorial. It worked out very well. I replaced the flex coupling and used the old one to adjust the torque adjustment. The square shaft of the inch pound torqe wrench fit into one of the ends of the flex coupling. I did manage to place the steering box in place by myself without a jack to help. Not the easiest thing to do.
Tom