Suggest you read the Pardey's The Cost Conscious Cruiser
as well as Annie Hill's Voyaging on a Small Income.
There are very few small boats with more than 6' headroom. After reading up on what you're looking for, you'll likely just have to go down the list of available boats and see what might work for you.
Some older (but costly to maintain) boats with deep draft also happen to have quite a bit of headroom but typically they are race boats and not really built for cruising. Else, you would typically end up getting into a very large boat to get more than 6'8" headroom.
Our boat was originally custom built for a guy who was 6'4" and he had it built with 6'5" headroom in the main part of the boat. The naval architect worked out the numbers and...it ended up being 54' on deck to accommodate the required headroom AND have a fairly shallow draft of between 6' and 6'6" depending on how it is loaded.
Best of luck