I showed Gotoh-san these pics and this is what he said ...
"It is not an exact match, but as far as I can see from Karaham's drawing, it seems that it can be replaced because it is a difference of about an error.
To be on the safe side, please check the dimensional drawings on the product page of our website for yourself." His english is a lot better than my japanese.
I think what he means is a difference due to rounding, rather than error.
I'm going to try it on my next build with the American Standard flat mount rout. What's the worst that can happen? I've split about half the price in beer in one evening and I'll have an extra bridge.