Hi Ian,
Here's a picture of my grinder, I run on 3-phase hence the red plug on the floor:

According to Myford my grinder was built in 1969; unusually I have the original manual for the machine. To the left of the machine is a small stand I welded up to hold the accessories. Here's a picture of some of the accessories that I sent to Myford to confirm what they were:

1. Swivelling workhead
2. Angled wheel dresser
3. Travelling steady
4. Internal grinding attachment
5. Internal quill and nut, which agrees with what you think are the internal grinding quills
I also got a faceplate, 4 jaw chuck, spare workhead noses, two wheel holders and a centre, but no collets. I believe that the newer machines used standard collets (4C?) but the older ones used non-standard collets. So far I haven't really missed not having any collets. Both my workheads have DC motors, but I think later models used AC motors. Looking at your picture I'd hazard a guess that your swivelling workhead has an AC motor. Finally here's a picture of the back of my swivelling workhead to illustrate the two belts, the loose one is supposed to be 17.6".

I need to move the motor position to adjust the tightness. Rather annoyingly the belt lengths are different again for the normal workhead.
Regards,
Andrew