I have two 741 open units that I would like to learn how to convert to posi.

I could certainly pay someone to do it but I'd like to learn and at least give it a shot.

I'm salty about the 3.91 - it was supposed to be a complete 3.55 sure grip but the brake drums were froze so I couldn't test it. Once I broke it apart it turned to be a 3.91 open unit. First time I've really been burned buying parts from a 'buddy'.