I thought the idea of roundy-round was using stock parts. That said the 46 heads you have should be allowed as all the heads had screw in studs from 73or74 on.
I do not have any first hand experience in circle track but I can tell that you should not be afraid to bend rules and cheat because almost everyone else will be doing the same. I know a guy how used aluminum heads and intake in a factory stock class, none of the tech officials clued in as the magnet would always stick to the motor.
I have also heard of various methods to keep racers from claiming you motor ranging from oil placement on and in the motor during the race and other means of a more physical nature.