Fond memories of my dad's 61 Falcon.  According to the first link below, there were two bolt patterns: 4x4.5" and 5x4.5".  On the link, enter the bolt pattern to search for what other cars came with that bolt pattern.  Occasionally it shows the hub size.  (Pinto's are not listed but 4x4.25" can be entered to see what is out there.)
http://www.roadkillcustoms.com/hot-rods-rat-rods/Wheel-Bolt-Pattern-Cross-Reference-Database.asp?LugCount=4&StudSpreadInch=4.5&StudSpreadMM=
 
This linked forum has more Falcon owners which should improve your odds of finding somebody knowing the wheel sizes that fit in the fender wells.
http://www.fordmuscleforums.com/falcon-pages/