66 mustang wheels swap

Depends on what you call a hassle.

IIRC the front spindles on '66's differ from V8 to I6 so they need to be swapped. That being said the biggest problem is swapping the 4 bolt intregral carrier rear axle that the I6 uses to a V8 cars 8" unit to get the 5 bolt rear axle. It may be possible to swap 5 bolt rear axle half shafts later Falcons used but I don't have any specifics and axle length and bearing sizes need to be compared. StuK

No, you need a 5 lug 8 inch rear and 5 lug front spindles, I suppose you could redrill the 4 lug stuff but it wouldn't be much more difficult to upgrade to V8 5 lug stuff, including brakes,etc.