The new TAG 4-stroke class will be using the three new 250cc engines just approved by TAGUSA. The new Biland, Oral and Vampire. The engines are 34HP 13,000 rpm. They will run at 400lbs if run in one class. There will be weights for a Senior and Masters class which may run 370/410. There will be front brakes only for 4-stroke.
Your shifter chassis would work fine for this class Freeze.