Hi Trev and Fido, yes the 1948 one doesn't have the large hole for geny according to the 48 parts book. I would be happy with or without the geny hole but I bet it's a real pain if you have geny trouble to get it out of the one without the hole.
Trev if your mount is off the bike I would appreciate a few pics gflash11@hotmail so I can email around the place.
Fido thanks for the offer to draw around it etc it may come to that but next time you have it off, no rush. It's a long way off yet before I start on the 48 A7 I'm just collecting all the bits. I need to finish my A10 plunger first.
The worst thing is, I remember seeing those longstroke mounts at swap meetings (autojumbles)over the years and Iignored them. I think I even owned one in the past and got rid of it with other parts. I wasn't into longstrokes at that time and I didn't know that's what it was for. I didn't have the 1948 parts book either. I've had it in my brain that the mounts were all the same as plunger ones. Live and learn.