She is definitely a B4 with one or 2 differences. Yes you have a B1 front end with leading caliper mount but what about the caliper itself? I can help with the correct forks with trailing caliper mounts. The forks were completely different. Different bottoms, different tubes, different inners and different tops. I think they were slightly shorter too but I am not 100% about that.
You also have a G model front mudguard fitted.
I can help with standard size rings too.
Cheers
KK
