TooCoys, strictly by vintage your boat is a Florida-built boat and I'm almost dead certain HM changed the HIN format when they moved, in effect making the Alachua plant look like a different company (since for a time they ran both production lines concurrently). This was probably for internal-accounting purposes but does us owners little good for clarifying what we have.
I do know absolutely for certain that the humble little 27 and the race-bred 54 have virtually nothing in common as regards design or original purpose. Whoever reported that they do is guilty of post hoc ergo propter hoc. I personally worked on the design of the 54 with my dad, with my brother Steve, with Warren Luhrs and with my dad; all of us had substantial input into the design of the race boat Tuesday's Child (as in 'is fair of face') and into the design of the production H54 that came after. The race boat was designed in 1977-78 and the production model was not any reality before model year '78-'79 or probably more like '79-'80. I first saw a production H54 at Annapolis in '81 (and hated it. Another story).
Also, to my knowledge, none of the HM-assigned HINs reports an actual serial number, as in from hull #1 onwards. Throughout the industry these are coded as to production line, production year, production month, and sequence in that month; and that still is not enough for us to always know for sure which boat is newer or older than another. The Marlboro (NJ) numbers are more easily deciphered; but they're like dreams: too easily misinterpreted, and their misinterpretations too often spread far and wide as though definitive when they're anything but.
What I do glean from your HIN is that your boat was a December 1980 boat, probably the 24th hull of that production line that month. The 'M' designates a model year-- this is by law-- and the 'E' indicates the fifth month, with August being 'A' -- also by law. I expect the '549' is referring to the Alachua plant (they may have doubled the hull size as a kind of code-- that's a guess) and each number there indicating something else. Remember in Marlboro they had two lines of 25s; I never visited the Alachua plant but I know it was much bigger and for all we know they ran two or three of each model there. In most boat shops they can switch lines over to other models depending on orders; so the '5' or '4' might have indicated which line it came through even though that line may have been meant, at first, for the 30 or 25 or any other.
The best way to find some light in this tunnel is to poll other Alachua-built H27 owners and catalogue HINs, something I've been trying to do with Marlboro boats for years. It's a lot of data to collect and sift through and I haven't found the time.
I hope to spend some time with John Luhrs later this year and this is one of the things I'd like to discuss with him. More as developments warrant.