Yesterday I rearranged my garage and got my toys accessible.  The Harley got it's annual oil and primary fluid changed.  It doesn't get tranny gear oil change this year.  I put the battery in the Mustang and fired it up.  Took it to the end of the street and back.  Only put 500 miles on last year so no oil change.  Re-torqued the lug nuts as I bought new tires last Fall just before putting putting it away.  Glad I did...there were some that were loose.  The project car just got rolled around and admired.  I think the first things I will do is repair the cracks in the dash pad and get the rest of the interior parts (dash, steering column, rear interior quarter panels, rear package tray, junk tray) ready for adhesion promoter, primer, black paint.  I have to work in some gardening/weeding and other home projects, then a week in FL at the end of the month but I plan to make some progress in the next few weeks.

The first answer would be MONEY. Since you got no replies I took a cursory view. Kits seem to range from about $800-$2,500. In a post on another Forum someone mentioned that the earlier spindles were smaller. Oddly the kits show 71-80 Pinto so maybe they include a new spindle??? Be aware that a lot of the kits upgrade to the 5 bolt pattern. Also a lot of these kits are for drag car brakes that are thin rotors and likely not conducive to everyday driving. Both are something to be on the look for.

My personal recollection is that there are Ford factory parts that the swap can be done with. But off hand I don't have a list. I also remember people saying the whole (welded in) cross member had to be swapped??? Everyone wants the early, thin bumper Pinto, but there was a story on this site where someone had a later 74 Pinto and they swapped over the earlier body parts and it seemed easier than working around the brake/steering rack issues of an early Pinto. Sorry I can't be more help.

The Baby Blue color is a very '70s color, just today someone said they love the color.  I've yearned for years for the '71 gold color but I've learned to love this blue one....like you say, it works!

seem to be having trouble with copy and paste of link.
sorry.

https://www.ebay.com/itm/296393712768
Saw this one...so nice. My first Pinto was a '71, exact same exterior and interior, but vinyl roof instead of a luggage rack.
If only I had another stall in the garage.
This one has a reserve so will watch to see what it sells at.
Oh well.  At my age I've learned to admire, without having to acquire.
I've been thinking: why am I so drawn to this eBay car? If it was another color, it wouldn't grab me so much.  It's the color!  My first Pinto was this color.  What is it about color that gets tied up in the emotions?