These were my findings from a while back.
CSX2000 to 2200 - Smith Gauges
Large gauges – 4” (100mm)
Small gauges – 2 – 1/16” (52mm)
From 2201 onto 427 cars - Stewart Warner
Large gauges – 3 – ½”
Small gauges – 2 – 1/8”
427 Cars – Smith gauges
Large gauges 4” (100mm)
Small gauges – 2 – 1/16” (52mm)
Ammeter was Lucas
FIA Cars – fitted with Stewart Warner gauges at 2 – 5/8” for
oil pressure and
oil temperature and a 2 – 1/16” Ammeter-I do not know about the large gauge or gauges
It is interesting to note that the first one or two cars may have come with 5" speedometer and tachometer gauges. From Rinsey Mills book,
Original AC Ace & Cobra, 1990“Apart from the first one or two cars which used 2.6 Ace 5” main instruments, both the speedometer and rev counter were of 4” diameter.”
George