If the bore isn't bad & the piston are still good you could, hone the bore install new Zero gap rings, just run thicker head gaskets &/or shave some material off the pistons domes "If it actuially even has 12:1 pistons, but 12:1 flat tops with an open chamber style 906 head would be almost not possible, with out some serious head milling & O-deck or above deck pistons w/serious valve reliefs... Or Re-bore Deck & Hone the block, then get new pistons, then rebalance the whole combo... the cylinder heads intake ports & combustion chamber size & design, are also very important part of the combo too, for making any kind of decent power {really need to know "exactly", what's been done to them}, a good camshaft with matched, springs, retainers, locks, seals, proper valve sizes, appropriate rockers 1.5:1 or 1.6:1 & then the proper style, size & length of push-rods, intended for what your usage & the rpm range that you will need to be at... The weight of the car, the proper gears, converter so your combo work well for you & to make best use of the camshaft & cylinder head combo, are also very important to your overall cars combo... Over all lighten up any rotating mass/reciprocating weight, drive-shaft, rims, crank, rods, pistons etc... Weight of the front of the car &/or moved to the back, also Fiberglass hood & bumpers, then the Battery moved to the passenger side rear of the trunk & aluminum heads really get allot of weight off the front of the car, to help allot with traction & weight transfer... Then Suspension, Shocks & Light weight Rims & Racing slicks or Drag radials/Tires, also how well that they work & overall weight, is also just as important as the engine &/or transmission combos, to get the car working & the lighter the better, easier to get a lighter car to go fast... It's all about the power to weight ratios... From what it sounds like you had, if it was tuned properly, you possibly could have been in the high 12 second zone already, with slicks...
