302 to 306 i need a kit

Why just 306? Something wrong with the current rotating assembly/motor? Seems like a lot of work for 4 cubes. Maybe it's just me
 
im rebuilding the motor wanna change the pistons for the compression n i have a 306 in my 86 coupe n after tune adding a supercharger ill b around 500 hopefully i wanna get the same maybe more on this motor this ones gonna be carb