First, absolutely nothing is 100 % “direct bolt-on” for every 50+ year old car when you’re talking about aftermarket parts. These cars were definitely not all identical rolling off the assembly line. What bolts right on to one car may require modification on another.
Second, the brake line thing. I think my earlier posts made it pretty clear that if you switch from a distribution block to the later combination valve you’d need to modify some brake lines. The combination valve DoctorDiff sells is an exact reproduction of the original disk brake combination valve. It is a direct bolt on if you use brake lines made for a later disk/drum car. If you reuse the drum brake lines intended for a distribution block, you need to make modifications. That’s not DoctorDiff’s fault, if you use disk brake lines like you’re supposed to they fit fine.
Adjusting the brake light switch is something that’s required pretty much any time you change major brake components, that’s part of the deal too.
