Ray,
when you get full access to the bike, try to slip a finger between the battery platform mounting brackets on the frame and the cross member below. If your finger slips in to about the first knuckle, it is CA7 or GA10.
If the frame has only one set of cast lugs on the front engine mounts and a steering lock socket on the head stock and all frame welding is oxy-acetylene, I would say it is a 1955 frame.
On EA7, FA7 and GA7 frames, the finger test under the battery box brackets results in the finger tip only being able to be inserted.
As a matter of interest for some, frames were oxy welded until somewhere in the EA7 series, probably until the sidecar mount was fitted in the rear loop, and then were electric welded.
Trev.