You can run as a guest but the vehicle will be a race car meeting at minimum every safety rule for the speed it could attain. If not meeting any listed class it can run in “time only”.
Not to discourage you at all, but anything you build will be a “race vehicle”. There is no driving of a race vehicle on the lake bed at all period unless on the course in competition. Any build will meet every safety of its class and speed. A SCTA rule book is a must.
Let’s say you choose a 55 post Ford coupe with a 292”. That’s a D/Classic Prroduction coupe and sedan. Record speed 205+. That means your build will need to meet every rule for 200+ mph. A full roll cage similar to a NHRA Pro Stock, all interior upholstery removed. Racing seat, welded racing wheels, 200mph+ tires, minimum 3/2-15 fire suit, limb restraints, gloves, shoes, head restraint device, 2 separate fire systems, all glass replaced by lexan, etc.
With a little researching on the SCTA site under forms you can actually find an entry/ checklist that every vehicle uses and see what will be needed if it pertains to your class. I print one before every time I plan to enter my gas roadster .. pretend I’ve never seen my car car and go thru it line by line.
Tim McMaster, after building his own pickup, bought a legal roadster for his y-block to go faster and reach 200. I’m not telling you do it at all because of the fun I’ve had doing it with my family and friends for 45 years. What ever you choose will be fun..JD..