IMO the limiting factors should be horsepower (a simple and clear turbo rule, a/a, etc.), single tires, no hood pipes etc. There has and always will be purpose built competition vehicles in all walks of motorsports. A smooth bore charger capable of 1000-1100hp would be ideal to me. The rules need to be simple so every knuckle dragging truck puller in the country can understand them. Adding rules adds gray areas, which starts the *****ing. PPL has done a great job with the old 2.6 class, at this point any LPS puller can goto just about any organization and pull. Why fight growing pains for years when we can look at history and see what the final outcome will be?