I think you should be able to swap out the electrical/pin/switch portion of your assembly.
I also believe the 77 tumbler comes out with a paper clip etc to the side in the space between it and the mechanism. RTFM (?) If you don't have one, let me know and I'll look it up for you in the paper FSM I have.
Cannot advise about disabling the steering lock pin- we rarely lock our cars so I rely on that pin!
80 300SD (129k mi) 83 300D Turbo (230k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi)70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)