Hey JC,
I don't have an issue with Rock auto, I used them a couple of times but the shipping added up. Basically I get the same stuff through Advance(I use them alot for this kind of stuff I take advantage of the promo codes and free shipping) ,autozone plus some non chain local spots. Raybestos is a good name.
As far as a master The one you need would be the same one that would go on a 67 Mustang with 4 wheel drum brakes. I haven't bought one in a while but I bought a few from autozone for like $15 a piece with lifetime warranty( I think they are only 1 year now) . As far as the Cj line kits, I've never used one,I buy 3/16" brake line in bulk, so I usually make those lines myself,but I have the flaring tool,etc.If the kit is ceap it's probably worth it for you. It is possible for you to buy some shorter lengths of line with the fittings already flared on as long as you are careful not to kink them when shaping. For the rest of the conversion,You will need a 3/16" union, and a 3/16" plug. Most importantly you will need to use your current 65-66 pushrod with the 67 master cylinder to maintain a good pedal height. Good luck.