More 73+ disc conversion questions

When I swapped my Dart over I just used the lines off of my donor car.

However, I think the lines from the MC to the prop valve should work with a little tweaking. You might need an adaptor or two though, I seem to recall not all the fittings being the same size on the disk MC/prop valve as they are on the drum MC/prop valve. But I've switched a few cars over at this point and it might depend on the year of the car too.

No need to change the lines all the way back either, but again you do have to do a little "tweaking", I found that the line going back to the rear brakes is a little longer on drum/drum cars because of the size/shape of the prop valve. Not a huge deal, but its just long enough to make hooking it back up a bit of a hassle.

The 11.75" rotors are nice, but they also require the use of 15" rims, so swapping to them can get spendy fast if you have 14" rims still. Otherwise its just the rotors and $100 for the caliper brackets. The larger piston calipers are also nice, but I haven't used them on any of my cars yet. The two I've swapped to 11.75" rotors retained their original calipers, the Dart is getting a rebuilt set but I did the exchange with '74 A-body calipers.

If the calipers are in working condition, I'd just rebuild them. Most of the calipers out there are just rebuilt calipers anyway, and a lot of them now come with phenolic pistons instead of metal. If they're in good shape, I'd just clean them up and change the seals.