Do they make a complete disc break conversion for a 69 Dart

Yes, many setups and many posts here, and many choices to make (SBP or BBP). Scarebird's setup is cheapest and simplest, assuming you won't remove your spindles and control arms for other things (new bushings). You can also keep your SBP wheels with it. Wilwood allows either SBP or BBP in the same hub (thus can change later), but is quite expensive. It also works with your existing spindle and control arms.

Most posts here suggest getting the 1973+ BBP disk setup, but used parts are getting rare and expensive. You can buy all new parts (ebay), but almost as costly as Wilwood, for an older heavier design, and it depends on being able to buy the integral rotor/hub in the future.