I know that Chrysler sized their power drum brake car's brakes appropriately for the intended use, as to engines and trailer towing, etc. Meaning that a 318 car got the smaller sizes and a 440 and trrailer tow/genuine police cars got the 11x3s all the way around. BTAIM
I have always liked OEM-spec parts due to their obvious robustness of design and durability. As things have progressed, the availability of the "consumables"/wear items has dwindled from what it was when the cars were just "used cars", especially brake drums.
I would always trust an OEM design over an aftermarket design, no matter what, BUT for the uses we are using the cars for these days, such robustness can be over-kill, by observation. YET the future parts availability issues can be the winning orientation to follow. Which would usually lead to Wilwood. There ARE a few other companies which supply the disc brake kits, too. AAG and others listed in prior threads in here on that subject.
Doing the dual-reservoir master cyl is an easy bolt-on upgrade. Just need the related lines (usually in repro) and the 1967-1970 power drum brake master cyl.
So, to me . . . the conversion is more about future parts availability than safety or whatever. Which can mean "As long as it works well and meets your needs, no real reason to mess with it". YOUR judgment call.
Take care,
CBODY67