Waternut,
I'm 6' 3'' too, or I was the last time I got measured which was a while ago, and I've got an 84 Classic. There's not enough headroom for us longshanks in the old Classics, but I've adjusted over the years and rarely bang my head. It's a quandary like so many things in life. If the boat is otherwise a good deal, I'd go for it. I mean I'd really like more headroom, and I'd like AC, an enclosed head, a tuna tower and diesel power, but every boat is a compromise. I'm happy with mine.
Headroom is a funny thing. While even big cars rarely have enough, my Toyota Echo (the Urban Assault Vehicle) is ridiculously small and has oodles of headroom.
Good luck whatever you choose to do.
Mike