The east coast clubs seem to bend the rules more than the west coast clubs. You can run with SVRA or VARA.
East coast B/P GT-350 engines put out over 550 HP today. They made what... 330 HP in 65-66.
I would call the local club that you wish to run with and speak with one of their tech guys. They will point you in the right direction and welcome you with open arms.
Monterey and Coronado are two venues that require that the cars be truly vintage with a pedigree and period correct.
Rules & Regulations | SVRA
Vararacing.com