Before I did the disk brake big bolt pattern swap I had to find a set of wheel spacers that were approx 1/4" thick so the Chrome Slotted steel wheels I wanted to use would not hit the raised edge on the 9" drum brake. I could never find any that weren't a semi custom piece for big bucks.
The 5 on 4 1/2" spacers had a center hole that was to big to allow the holes to be slotted down to 4".
What I wound up doing was picking up a set that were for 4 on 4" and redrilling 4 holes to get the 5 on 4. This worked out fine and I gave them to the guy that bought the wheels.