There are 6 lug disc brake kits that are available for both the front and rear axles. I put a 6 lug disc brake kit on the front of my 1959 and absolutely love it. Of cours my Truck came from the factory with a V8 and very rare power steering, so I would never swap the frame.
I know this is the HiPo shop, but I still would like to point out there is nothing wrong with the stock suspension on these trucks. Of course people will tell you you have to do this or that and you can't do this or that, and have some pretty interesting reasons for why or why not. I like the way the old truck drives... like an old truck. This however is your truck, and you will be paying the bills, so do what you want. I just wanted to make sure you knew that there isn't some kind of law that says you have to cut up the truck to enjoy it.
Welcome to the Bolt!
John
