Alex,
Bruce would be right, this question belongs on the technical forum but well let you slide this time since the forum was just "upgraded" or "segregated" in order to promote harmony among the participates.
I too have a 66 CDV, the rims are 15 x 6 with a 4 inch backset and there is very little clearance at the rear skirts, maybe 1 inch. The RWD Fleetwood rims from 1986-1996 are the same and can be used if so desired.
Most aftermarket rims start at 7 inch because the newer cars have more clearance at the wheel openings. very little interest in 6 inch rims.
You can upgrade to a 7 inch rim at the rear but they would have to be fabricated custom with a five inch backset.
Heres a link to American Racing for 86-96 RWD Fleetwood, none of which will fit on your car since the are 7 inch rims.
http://www.americanracing.com/appguide/third.asp?Make=CADILLAC§ion=app&car=112_
Go to
www.jegs.com and look up wheels, you can contact various wheel manufacturers and see who can fabricate custom rims for you with a 5 x 5 bolt pattern, any size you want providing it will fit and you have deep pockets.
HTH,
Porter
