I was broke (still am and most likely will always be due to my hobby)
cheapest way is rebuild the drum brakes (but go to dual master for safety)
money wise, it's a tossup between 73-up and a conversion anymore.
next cheapest way is to piece it together for the disc brake upgrade. I did the scarebird brackets using the original 9" spindle and hub from the drums and had the autoparts get the rest piece by piece as money came in.
Yes ,you can stay small bolt pattern wheels if you get the rotors drilled at a machine shop (or use the supplied paper pattern, make copies for future use if you want to) my cost was 25.00 for both. that was using scarebirds brackets and auto store parts only, not their kit. my cost was easier to bear since it was piece by piece.
most of the other kits I have seen or used have a center register that can be a problem using you old wheels, there is supposed to be one kit that's a copy of the 73-up parts and a bolt on but I have not used it or seen it work on early A's yet.
here is my setup. yeah I had the hub drilled so that I could go large bolt pattern also but I rolled the car around on the small bolt pattern studs for a long time before re-drilling the front hubs to LBP.