My research has discovered the following points :
Point # 1 : MA know nothing of the B arm being illegal
Point # 2 : The only place this arm is illegal, according to some, is this forum
Point # 3 : Somebody supposedly got barred from an event because of the arm. Till this day nobody can name the event or the entrant.
Would you be prepared to put together a Statutory Declaration confirming that you had one fitted to your B in 1977 as I have it on very good authority that is all that is required to get this over the line.
Cheers