OK, so fitting 18" wheel centers in 19.5" wheels won't work at the drop center.
There are no 17" dual wheels with the distinctive 18" lots of hand hole dual wheel look that I know of.
There is still hope though chances are the backspacing won't work out even if an 18" center would fit in the 19.5" rim. So, with luck the center will intersect the rim somewhere other than the drop center (it will) and where it does fit might give correct backspacing. This is probably a long shot though.
The center could even be turned down to intersect where you need it to give proper backspacing, if there is enough material where it's needed.
Let's still find the depth measurement on the 18" wheel dish and I'll do some measuring and comparing to a 19.5" rim.
Grigg
