Bill,
I replaced my front drums w/ disc’s this last Fall. Not to hard – make sure you bleed the system well – a pressure system works best. The change helped my car a lot. Why are you going hydraulic? The system w/ the disc’s works great. If you are on a 73 It should have a dual MC in it and should work fine – just bleed well. I think all the hydraulic systems come w/ their on M/C attached so will not require the one you have – anybody correct me here if I am wrong. Seems to me you have everything you need now to stop your car – why not try it first then go the hydraulic route if not happy? Where are you located? Let me know if you need any help,
Dale