Here you go, Piston area and force.

Bore size is one of the ultimate main limiting factors to hp but for most were not making enough hp to overly worry about it, most aren't even pushing what a 318 bore is capable of and really a 360 bore is less than 3% bigger than a 318 bore and a 340 bore is slightly more than 3% compared to a 318, even a 273 bore should be able to handle 400 or so hp without crazy work. For most bore size ain't a huge issue, making power at an reasonable rpm for that person is probably a more pressing issue for most which usually mean a higher power to cid ratio aka no replacement for displacement.