Well my car is a conversion, so my answer is not what you are looking for, but it interested me after seeing your post so I measured it.
I have a modified custom mount and we actually played with it in a couple of variations. First I was concerned about shift rod clearance. Secondly I was concerned with sheet metal fitment.
We finally settled on matching the sheet metal to the engine bay gasketing and shelf, which gave me plenty of clearance on the shift rod.
After all was said and done, measuring like you did in your photo, we are basically dead on together...
My measurement matches yours as shown. FWIW...