Saying 32mm and 40mm are the same at the intake is too broad a stroke, and as you said the billets, well some but not all are also smaller. Since I run a 16/16 carb I, like you chose a 40mm steel intake and took the dremel to it. I really liked the cast intake but thtat 14.5mm intake made no since to me, and hogging it out leaves it pretty thin walled for cast.