Joe,
If you had the original chassis and it was wrecked you could transfer the numbers to the new vehicle (this is the basis of the heritage MG, Triumph and Mini re-shells) bit whether the FIA would allow it is a different thing. Are you going for App K in order to enter the European Touring Car Challenge?
If so I suggest you contact the FIA direct.
As to Homologation parts you only need to go to the MSA and pay your ten or twenty quids and they will gladly send you a reasonable facsimile of the certificate. (It'll be quite a thick book so "facsimile" in this case means "copy".