I have the JME insert in my '65. You should find that the opening in the metal is the same. Not sure about the gauge sizes as I did not go that route. If I was to do it over not sure that I would do the JME. Very expensive and you could do about the same with the '66 gauges.
TG '07 GT Vert with Saleen Racecraft suspension, GT500 exhaust, lightbar, silver painted stripes, 3:55 rear, 18" polished bullitts, MGW shifter, mirror with temp & compass.
'65 FB Shelby clone, 5 spd T5, dark blue with silver stripes. Added 4 pt roll bar and FR manual rack & pinion. Has JME dash w Autolite Phantoms, Torq Thrust D wheels, aluminum dash, etc. 14.2 sec in 1/4.