I may have missed where a 14 inch intake runner was introduced but I certainly do not agree with that.
However, I can agree with this above picture from the early 80's. L20B four cylinder with 50mm Solex carbs, 14.2:1 compression ratio with a 9200 RPM limit. The L20B FIA head does not flow as much air as the SR series head is capable of. Kinsler, in fact, recommended the 50mm as the bare minimum for a high performance SR engine in the conversations he shared with my Dad. (This was talking about the 54C head after I sent pictures to Mr. Kinsler to pique his brain) To add to the confusion, my Dad did not have the benefit of a cross-flow head that we all do now.
Now, I understand I don't have money to build any of these fancy things but a page taken from the past can help learn from either mistakes or triumphs.
But, once again, what do I know? I don't own a fancy engine so how credible am I really?
EDIT: I am just presenting information. That is all.