What Dave said, plus...............
For it's time, the knee action suspension was an innovation. But, quite frankly, it left a lot to be desired. The hard core restorers (if you can imagine ) will fix them because "it's the proper thing to do". For people who like to actually drive, and enjoy, their cars, an update would be in order. Probably the "pioneer" in old Chev disc brake kits is Butch's Rod Shop in Ohio 513-746-1113 (doesn't have a website ) if you're dead set on keeping the knees.
Otherwise, Chassis Engineering www.chassisengineeringinc.com has an excellent setup for your particular car. Just keep in mind that the stock MII 9" brakes would be marginal.

Which brings me to emphasizing what Dave said. Too often in rodding we tend to focus on appearance and power before the basics. After all, that's what strokes the ego (look at SOME of the rat rod stuff as an example). But brakes first, and suspension second, are basic to the pleasure, reliability, and safety of our rides. As much, or more, thought, effort, and financial commitment should go into the undercarriage as anywhere else on the car. And related to that, some will recommend doing a "front clip", say from a camaro or nova (same thing in many years). This has been done a lot, often times wrong. Hacking off a front frame section from your existing chassis, and burnin' on a "new" one from another car is not a novice level deal (see comment above about wrong). To do it correctly is much harder than a lot of people make it sound, and definately harder than it looks. And a botched job here ruins the whole chassis, and ultimately the car.