Stroking a 318 to a 390

That’s my thoughts, too! But if the deck height is 9.60 (I'm suspecting its taller) they would have to be milled .099 for zero deck. If setting up for a .038 piston to head clearance to achieve some resemblance of quench, the chambers would have to be in the neighborhood of 76 cc's just to get the compression to pump gas level. So if it's even a possibility with the pistons, the bare minimum would be a premium pump/low lead AvGas blend . Half of the 3.13 inch diameter by .05 deep (6.3 cc's), .0705 deep (8.9 cc's), or .100 (12.6 cc's) deep dish (my pistons) would become part of a dome along with the outer edge of piston above the rings outside of the dish. But the 536 gram pistons would be down to a lightweight if there's enough meat for it to be milled off on the valve side. One think I do like about the stock pistons, though. The possibility of reversing the pin offset to help reduce the side loading from the 1.53:1 rod ratio.