FWIW, I did get a response from Yamaha on the 450:
"The FG450 would have been made in the early 70's and not available in the United States. The serial # indicates that it was made 05/10/1972 and was the 198th one made that day. It has a solid Spruce top, Ovangkol back and sides, a Nato neck, and a Rosewood fingerboard."
Going on 34 years old and nearly spotless, it's definitely a keeper.
The 180 is definitely a 67, as I bought it new in Nashville in 1967, and the serial nr is 700xxx - the last three digits are handwritten in either pencil or black ink.
For anyone who's never seen the 180, here are links to pix of a good (but not spotless -- two years of college and several deployments on this one) example
http://www.pbase.com/joe_tn/image/53686049
http://www.pbase.com/joe_tn/image/53686050
Yamaha says (as does everything else I've read) that the 180 spruce top is not solid -- but I'm darned if I can see laminations around the sound hole. Wonder how many plies in a guitar top?
I'm enjoying this board...learning a lot. Now if I can just get the fingers back in shape
Merry Christmas to all,
Joe