Some 15 years ago when I first aquired my AUD MK2. I had the same problem.
My solution having no oxy gear was to cut and weld an old whitworth spanner to do the job.
Even with this spaner, it was still a pain to tighten up.
I am planning a much overdue overhaul of this machine soon.
If my (metric) crows foot set won’t fit, I will use the welded spanner to get the bolts off again, but then I am thinking that I will do one of the following:
A) Machine 2 custom shlouder bolts with long shanks and a metric hex on the end.
B) Use long versons of whitworth bolt and turn some spacer tubes ( to bring head down below the bed)
C) Possibly (if available) get a pair of hex cap head bolts. (I suppose I could re-thread a larger metric hex cap head bolt) I would then use a hex adaptor in a ratchet.
Anyone have any better idea’s.