I assume you are referring to the older, John Alden designed B35 and not the Bristol 35.5. The earlier boat was available as a Keel/centerboard, or full keel
Either way (and either boat), you can sail her without the CB, no problem at all.
On the older boat (as any), make sure those balsa cored decks are solid and in good shape. Bristol was a very good build, you should be OK. And then all the other little things.
I do not think the Keels was ballasted to any significant extent on any of the Bristol's. Certainly not to contribute to stability. The CB on my Hood
38 was only something on the order of 400 lbs, compared with 11,000lbs of ballast in the Keel
Beautiful, classic design. A bit narrow beam by today's standards, might not be the most comfy liveaboard
, but certainly a sea boat.
Hope this helps