I've only run Stock/Street, but my reading of the rules seems to state you don't have to jump all the way up to Street Modified, but instead can jump only to Street Prepared. I don't know what a "Stage One" clutch is, but Street Prepared Section 15.10 states:
O. Any metal clutch assembly, metal flywheel, or metal torque converter that uses the standard attachment to the crankshaft may be used. Non-metallic friction surfaces (e.g., clutch disks) are permitted. Dowel pins may be added. Any hydraulic clutch line may be used. Replacement or substitution of the clutch slave cylinder is permitted.