Do you only have one set of valve reliefs? Most replacement pistons have four notches, so there doesn't need to be dedicated pistons for right or left bank. Either way, there should be a small notch cut into the top of the piston that is supposed to face the front of the engine. There is usually the letter "F" cast into the skirt area of the piston, also indicating "front".
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!