Well I am new to the site/forum as of today and saw this post. I am not sure where you got with the project but the one thing I don't see mentioned it the possible swap of the wiring harness. I was going to attempt a similar repair to an old Murray I had but decided against it when I discovered that the original ignition switch on the Murray did not have a 12V switched source to use to power the solenoid. I am not sure if this is the same in your case but hope you were able to complete the project.