...and the pistons are pretty close to top.
How close? Have you measured with a dial indicator? .030" doesn't really "look" like much until you measure it. If you're < 0.040" under the deck I'd be really surprised to be honest...318s were always built as bread and butter engines with lower compression and zero performance options, so no money was spent on researching and developing better pistons for them from the factory. And with manufacturing tolerances being what they were, some engines were as much as 0.080" in the hole because the decks were marginally taller than spec distance of 9.6"
The KB167 is the flat top piston they offer...it's a hypereutectic flat top with generous valve reliefs for bigger cams. They come really close to the deck by comparison to stockers...and that helps your quench. Quench = turbulence in the combustion chamber, and reduces potential for detonation even with raised compression and iron heads; it also reduces need for heavily advanced timing. In a nutshell, the closer you can run the piston to the cylinder head deck surface without touching the better. Generically speaking, a street engine operating below 6500rpm with stock rods and < 3.5" stroke can be run about .030-.035". Better rods can facilitate a closer quench measurement...sometimes as close as ~0.020".
If you want to keep the stock bottom end to include the pistons, I'd personally recommend squaring/decking the block to blueprint spec (9.6") and running a thinner head gasket to put the pistons closer to the heads. If you are running stock heads-what year/casting number? Do they have the relieved chamber? If you can, maybe pick up a set of 302s, do a little bowl work, drop in some 360 valves (1.88/1.6) and a clean up cut, then bolt them on. Otherwise, you could also pick up a set of Magnums and do that conversion...only problem there is converting the valvetrain and unless you bought a set of EQs, you'd have to buy the Magnum intake too. All these parts add up quickly.
Keep in mind, this is only MY opinion...you can go whatever direction you'd like-just do some research and you'll likely find an avenue you can afford, and will give you what you're looking for. Also keep in mind, the greater amount of power you want, you'll have to upgrade everything else to work well with it...e.g., stall, gears, better brakes, subframes, suspension, etc. If you build a 350-370fwhp 318, you'll soon find any weak links...
