Do you have a copy of the proper SFI specs and diagram? If not I'm sure that will help you a lot scope up
The funny car cage is needed for sure, is the existing cage mild steel or chromemoly?
I think the main cage has to be chrome moly to be able to certify too SFI 7:50 specs confused scope up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)