Im a little confused with the 4 cyl rules at barrie and sunset....If were allowed to bore them out but the motor has to be "stock" what are our options for legal pistons??

We are allowed .30 over pistons and rings my friend..

yes, but can they then lightweight or flat top...because now they arent OEM and there a hundreds of options...whose to say one is legal and one is not

All the manufactures make a replacement piston or they are available from an after market company . If your motor came with cast dish pistons you can not replace them with forged or flat top . I will bet most the tech guys cant tell the difference between a forged or cast piston simply by looking at the tops of them with the head off . How ever they can all read a compression gauge .
Most the Jap OEM pistons are more the tough enough for racing and after you have decked the block and or milled the head your going to be maxed for the compression rules . Remember there is almost no performance gain from boring the engine 25 or 30 thou . A better way to gain performance on many of the 4 bangers is to work on the water jackets/ pump and use a better rad so you can lean on the motor harder with out it getting hot  ( #1 cause of melting pistons). Rather then spending hundreds on forged pistons try slowing down the water pump (pulleys from 20 bucks and up) since most of them spin too fast because they were made for street conditions .

thanx JoeChance.. I am looking at engine options for next year because when the track did a compression test on me it was very low and i need a way to bring it back up, and im not that expeienced when it comes to engines internals.