71 Demon 5x4.5" front disc swap questions

If I was going to the larger bolt pattern I would find a pair of 73 up a-body spindles at least. FMJ will work but anyone coming behind you will have a hard time figuring out what replacement parts to ask for. Imagine that getting much worse with Some Ford and GM pieces in the mix. its tough enough getting the correct parts from todays part stores already.
Even if you resort to aftermarket tubular upper arms they will use the stock serviceable parts. Just my .02 Good luck