First of all, welcome to the site. Youre in the right place for any info on these trucks. When it comes to disc brake/5 lug conversion,
www.earlyclassic.com is a great place to start. Give them a call. The guys there are VERY helpful and willing to answer any of youre questions. High quality parts and great costomer service. Several other places sell kits, but my recomendation is Early Classic.
I installed a painless kit in one of these trucks and a couple chevelles in the past. I recently bought an American Autowire kit and it is much more complete than the painless kit. It's worth the extra money IMO because you dont have to reuse any 40+ yr old connectors. Got mine on EBAY for about $460
The great thing about these truck is that there are alot of parts available from alot of different places. Everyone has their preferences, just thought i'd share mine with ya. Nice looking project, have fun