what pistons to run with set up??a bit of help

The KB 167's and 302 heads are a pretty popular combo. Have the block zero decked, and you'll end up with 9.5 or so compression. Make sure there are no sharp edges in the chambers and you should be fine on pump gas.

I would at minimum upgrade to 360 valves, and do a basic bowl blend and gasket match. With a fairly mild cam like an XE268, reasonable carb, intake and exhaust, 325 HP at the back wheels should be easily possible.