BobH,
Not to worry, I can make up custom orders too.
If you are going with 3" spacing for your somewhere in the middle of 1/4 and 1/5 scale, 5/8" spacing is close to the middle of 1/4 & 1/5 scale and is the same spacing as my 1/3 scale
2" spacing. It's actually 1/32" smaller. The exact middle of 1/4 and 1/5 scale is 21/32" spacing for 3" full scale. What ever your scale is, it can be worked out.

Email for more info for a custom order if you are interested.
[email protected]

ZZ