disc brake set up

so cheap disc brakes go hand in hand with upgrading to big bolt pattern, which sounds like something you don't want to do-- both from a financial stand point and the amount of work.

so the cheapest way forward for you, would be to track down a good condition 67~72 disc set up. this was you get to keep your upper control arms, and all you'll need suspension wise is a new set of lower ball joints and everything is a direct bolt in.

while there are known limitations of the 4-pot kelsey hayes system, it's a decent system and will work for you, what you are doing and meets your criteria.

two other options exist:
1- tracking down a used aftermarket disc system. one glaring problem here can be parts availability, even for small things like bearings, seals and pads.

2- upgrading to 73~76 front discs and using small bolt rotors. this would probably be the cheapest way forward but also has several stumbling blocks.

• you'll need 73~76 upper control arms or the upper ball joint adapter sleeve
• you'll need lower ball joints
• the rotors (to my knowledge) are only avail from dr. diff
• you'll likely need to grind on the caliper body to clear the rim if you're running 14"

the good part of this is that the 73~76 stuff is widely available and cheap.

no matter how you slice it, inherent in the swap you're going to need a master cylinder, hoses, lower ball joints and some hardware.

plan on spending something like 800~1K to get it all done. this number doesn't include rebuilding any of the suspension components, which you may find to be needed when you tear into it.