if you are going to change pistons you will most likely going to need to rebalance crank and if you are going all in likely recondition rods polish or grind crank....new rod and main bearings...not sure how deep you want to go....
I was in a similar situation as you last year. Add up your possible costs. When I did the math for just a few hundred more I got a scat stroker kit for my 318 which came with crank, pistons, rods, rings, bearings . My little 318 grew up and its now392 cubes 0.040 bored 318 with 4 inch stroke.
