Hi again Eric,
There is less difference between the two types than appears at first glance. The longer 1927/28 type with sloping shoulders, is 12″ long overall, and 10.5″ between fixing bolt centres, whilst the later, standard type is 10.75″ overall, and 9.5″ between centres, so there is effectively only an inch difference, which is about half of what I was expecting to find!
Hope this helps.
Brian
