I emailed the Record guys mentioned in the British Steam Car thread, about setting a recognized record for the "Worlds Fastest Packard Powered Post War GM Product" this was the reply
Dear Mr. Rich Fox,
To have your record attempt recognized by the World Records Academy, the certification fee is $2,995 if you pay after you set the record or $1,995 if you register in advance (2..3 months).
After you pay the registration fee, you will receive our official forms which you have to return to get your world record certificate.
If you want to order this service, let me know and I will send you an invoice.
Regards,
Tom Howard
World Records Academy