what is your intended use for the stang? street, strip, autocross? There are lots of different options out there for all sorts of budgets. If you're going the restomod route, that opens some options. For something more budget-minded and OEM style (but improved), there is the opentracker products. If you want to go coilovers/tubular
control arms, there are a variety of choices: TCP, Global West, Street or Track, etc... Disc brake options range from Granada brakes to Wilwood/Baer systems. CJ pony has some package deals already put together, IIRC. There are also the Mustang Steve and Vintage Venom kits that allow you to use disc brake kits from 99 and up Mustangs. This should help you start in your research.
I will say this...Really take a look at your intend usage and budget. Plan your whole build out, phased over time and as money allows. This will hopefully keep your build on track in a focused/organized manner. If you don't, it is very easy to overspend, become overwhelmed, and have a project that does not progress.
Most importantly, do some reading and have fun! There are a lot of great resources on these forums...they have most certainly helped me out along the way.
Matt