the only rule that i can think of is motor restrictions. that rule was made to keep the same thing from happening to ardc as what happened to usac, nema and, i guess you could throw most everyone else in there as well.....the obsolescence of the pushrod midget motor.....and the manufacturers changing the rules when something faster comes along. (read as cost savings and more racers at the track)
the only restrictions on motors are that the esslingers have to be small blocks and nothing over 166ci. that leaves it open for mopars, hawks, and yes, even the toyota (so far)

as far as mr buckwalter....the motor he runs in the midwest is not the same as the one he runs with the club. he probably couldnt afford to run it at the club level cause with the extra HP comes less reliablity and more frequent rebuilds and, frankly, he doesnt need the extra HP to win with the club.....he wins with his setups, driving and smoothness.

i personally dont see the point in having a field of cars where 95% of them have the same chassis and motor....plug in a driver and bolt the right pedal to the floor and see who wins.....racing is suppose to be about staying within a certain set of guidelines but having the latitude to make changes and be a little different. i dont see a whole lot of that anymore. and its a shame.