As to R12 vs. R134a...you can get a Sanden compressor the is rated for R12 use.My old 1992 Dakota (RIP) used R12 with that style compressor, which is still available.There are R12 models in the Sanden replacement catalog also.
Hit it with weld thru primer and do it up before.Make note of where all the voids are that aren't accessible and mist in Fluid Film to stop rust.
https://www.fluid-film.com/
It's not a kit...just the box.I will be purchasing the Bergman no cut coupler BAC No Cut Steering Box Coupler - Bergman Auto Craft
and the wire bail retainer from DMT Mopar A B E Body 66-73 Dodge Plymouth 3" STAINLESS Steering Column Coupler Cover Clamp / Retainer
I am going to wait...
You might try a Borgeson box also.I got one with a 10% off code from Summit Borgeson Universal 800127 Borgeson Mopar Power Steering Conversion Boxes | Summit Racing