I haven't done a disc conversion (yet) and wouldn't buy a semi-nameless *kit in a box* setup either.
Here's a couple links. Both are places that cater to '55 / '57 Thunderbirds but since many of the brake parts are (hopefully) interchangeable with full-sized cars of the same years I'm passing them along just in case...
https://www.classictbird.com/ .....(740) 622-9700
https://hillsresto.com/......(740) 949-2217
They both sell (dual master cylinders) and install their disc brake kits in their own restoration shops, so they know the in's and out's of them. The several times I've called for advice and assistance they have been very helpful, give their Tech Support staff a call.
Ask about self-adjusting retrofit kits for drum brakes also.
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