I think these apply to you, someone correct me if I am wrong.
Endurance GTL:
Vintage Light, Formula Two stroke, NuSpeed,Other bikes up to 500cc four stroke and 350cc two stroke not included in sprint classifications.
Formula 2 strocke
Lightweight:
125cc GP Style Machines
350cc Liquid Cooled Street Based Machines
500cc Air Cooled Street Based Machines
250cc Water Cooled Single
400cc Air Cooled Single
The 300 is a four stroke twin... Endurance, maybe.
Bakaboy any links to information on those classes? I'm not seeing them on their website.