How to word a box charger turbo rule

Long story short, I have lots of interest in my area from guys about building a 2wd diesel class. We are trying to keep this an inexpensive class as many guys are mad about how far out of control our local workstock and 2.5 classes have gotten so we are hoping to keep this a box charger class. The rest of the rules are fairly simple and straight forward. One ton rear end and drivetrain, single 35 inch DOT tire, rigid suspension allowed, common weight obviously once we can decide on one and all the safety stuff (loops, killswitch etc.) My question is how would you word a rule on box chargers? Goal is to limit it to an s300 frame with a t4 flange, either s363 or s366. No billet or aftermarket cast wheels. How should the MWE be worded? I haven't messed with a box charger in a long time so forgive me. Just trying to create a fun, somewhat budget minded class for people who don't want to dump boatloads of money into a vehicle.