Yup, so many options depending on how much you want to spend and what look you want to have. I'd upgrade those 9" spindles regardless of what system you decide to get. The wheel bearings are just too wimpy IMO. As mentioned, do you want to keep the small bolt pattern, keep the rear the same, have two different spares? With disc brakes, you're going to have to 86 those 13 X 4" wheels regardless. The stock '66-72 KH disc brakes are pretty much a bolt in if you can find a donor car. If you want the big bolt pattern factory discs, a '73-6 donor works the best, but, there are other B,E, and F body stuff that can donate some parts. There are also many different aftermarket kits with a whole variety of options. If this is going to be a driver, I would recommend a kit that uses off the shelf wear parts and not proprietary stuff. It makes getting replacements a lot cheaper and easier.