Dwayne,
FoMoCo indeed used the 5x5 bolt pattern. Heres a list of the ones that did.
FORD FULL SIZE (CUSTOM, GALAXIE, T-BIRD) 73-78
FORD Custom 73-78 FORD Galaxie 73-78
FORD LTD 73-78 FORD Thunderbird 72-76
LINCOLN CONTINENTAL, MARK III 73-79
LINCOLN Versailles 73-77
MERCURY COUGAR 73-78
MERCURY Grand Marquis 73-78
MERCURY Marauder 73-78
MERCURY Meteor 73-78 MERCURY Montclair 73-78
MERCURY Park Lane 73-78
Found this out the hard way when i found a very highly sought after Lincoln Versailles rear, (9 inch disk brake same length as Fox chassis Mustang) and was very perplexed when my trusty 5x4.5 Mustang wheels wouldn't fit! It looked awful funny with Buick wheels on the back!!! Hope this helps!