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It was very late, but I remember reading something last night while I was researching about the later round-port A12A and A14 heads having the old-style 1200 A12 bolt pattern. If this is the case, then this is the head I want. Is your head a later model round-port? If so, is it the one with the casting codes front 454 and rear 990 or something different?

Ideally I would like the round port high swirl head as described on the cylinder head wiki page. The casting code info is not there yet for this head, the 454/990 head is the regular round-port. This high-swirl head is the one with the unobstructed intake ports which are "lowered to cause the charge to swirl as it enters the chamber". I am after low-mid range pull and fuel economy.