I replaced all 4 drums on my '68 Convertible with SSBC hevy duty conversion kits. Front and rear cost about $2000.00, and the kit made it very easy to install both in on a Saturday afternoon. After doing this I found a website that recommended junkyard calipers or even factory replacement calipers up to 1982 that will bolt-on..
Disk Brakes make a great improvement over drum brakes, but next time I'll try Checker or Autozone for factory replacements 1st..