this is the way CAMS approval works:

log book/pre-race inspection is only to check eligibility of the car and that it has all the required safety gear.

the cage is registered with CAMS seperately, before the log book/pre-race inspection. A CAMS Cage Registration form has to be signed by the cage builder to certify the materials used and the welding and workmanship. A reputable cage builder should have the forms, otherwise you have to contact your CAMS state office.