It seems like every online wheel dealer I look at doesn't allow me to search for a 1968 Cadillac. Any idea what other vehicles have the same size wheels as a 68 Deville?

 

GM tends to have the same size wheels on all cars of similar chassis and configuration.
They were made from 1965 to 1970, the 4th generation and probably other GM full size cars of that period are all pretty similar.

 

It looks like the bolt pattern on a 68 is 5X5.5, upon further searching I've found that newer dodge's (magnum and charger) are also 5X5.5", anyone have any idea if wheels off either of these cars will work? Backspacing wise anyway?