The cause of all this trouble is I have the copilots panel,and
it appears that they were all made for the bigger boost and cylinder
head gauges.
What they then did, was cut / hack, the webbing between the two gauges.
From period photos,a couple of flat plates to hold both boost and both
cylinderhead gauges, bolted at either end.
Here is the rub,the boost gauge plate is smaller (as the early boost type
is a unique size!)the cylinderhead temp gauges the normal3 1/4.
Your idea of a plate/adaptor thread is a good one.
Thanks for your help.
Cheers Mike