KB167's aren't for magnum (well, they can be but that's a whole nuther ball o' wax) so you'll need to choose a different piston.
i don't understand the phrase: crank will be stoked with...
personally, i'd say if you're saving up for a stroker kit just run the stock pistons. do rings/bearing & cam bearings and a hone, clean everything up and ship it.
any particular reason for the 509 cam?