A quick read of the NASA rule book, it looks like you would be in the Super Touring class.
Non-Production” vehicles (ST1, ST2, and ST3 only), include all other ST series eligible vehicles including “kit” cars, purpose-built track/race cars, tube-frame and partial tube-frame conversion vehicles, and “Production” vehicles that have modifications not in compliance with section 6.2, and will be assessed the “Non-Production Vehicle” Modification Factor listed in 6.5.2 unless the vehicle model is listed in Section 6.5.3 of these rules and has been approved to compete under “Production” vehicle status. A competitor with a vehicle originally qualified as a “Production” model may use the Modification Factor assessment for “Non-Production Vehicle” to avoid all “Production vehicle only” limitations/restrictions in section 6.2.
Looks like a BHP/Weight formula
Super Touring 1 = Adjusted Wt/HP ratio equal to, or greater than, 6.00:1
Super Touring 2 = Adjusted Wt/HP ratio equal to, or greater than, 8.00:1
Super Touring 3 = Adjusted Wt/HP ratio equal to, or greater than, 10.00:1
Super Touring 4 = Adjusted Wt/HP ratio equal to, or greater than, 12.00:1
Super Touring 5 = Adjusted Wt/HP ratio equal to, or greater than, 14.50:1
Super Touring 6 = Adjusted Wt/HP ratio equal to, or greater than, 19.00:1
More at
https://members.drivenasa.com/rules