Hi, I am thinking about getting 17" Cragar SS wheels for my 66 (17x8 front and 17x9 rear). I think the 17x9 wheels come in 4.5" and 5.5" bs. Which would be better for 275/40/17?

Ideally, 5" would be right for a 17x9 but 5.5" would work.
Sure you can't get 5"?

I put 17X9 with 5 bs on my 69 with 255/55/17 and they fit good but if they were any wider they would hit the lip.