Not sure if you are going for Resto, or Restomod or Race car... The spindles DID change on later cars. Those later spindles can be easily fit to your car and allow for a wider set of disc brake options (and bigger bearings, options for dropped spindles, etc.). I did that when I converted from drum to disc using Magnum Force spindles and I'm really happy with the outcome, but it is also possible to just use stock later model ('73 and later) spindles. Just a thought.
Just a couple other random things to remember (excuse if you already know these or it doesn't matter on your conversion): If you change to disc in front and drum in rear the braking is a little odd as the drums are a self energizing design and the discs are not. I needed a proportioning valve to straighten this out until I switched to four wheel disc. If you do change to four wheel disc, the rear wheels bearings change (I think on all the early mopars) from the stock style to the "green bearing" style, that is, from the angled bearing to the flat bearing. The flat bearing is by many accounts actually less good than the factory style. I changed over and haven't seen any negative effects yet even after a couple of track days and driving like a moonshiner when the mood strikes me...
