The '97 and later Ford wheels are what's called "metric" they will not fit earlier Fords.
The '96 and earlier F150 wheels, with the exception of the hub cap lugs work very well on the '40 and later Fords.. The F-150 wheels will generally be 6.5" wide and are HD wheels.. This type of wheel is easy to spot if they do not have tires on them.. The rim will be stamped with 15x6.5, Ford and the weight rating..
I have altered the external lug wheel to accept the small early Ford hub caps by brazing a "knob" into the hub cap recess, grinding to size. The external knobs are not that noticeable once the hub caps are snapped in place...