If you're running a 1978 440 with stock pistons, your compression is low. VERY low. Like a calculated 7.8:1 low. I know, I've been there. It's not the deck height of your block that's the problem, it's the compression height of those stock pistons is soooooo low. An aftermarket piston will be taller, thereby increasing your compression ratio. With the super short mid 70's 440 pistons, no amount of milling the block or heads will get you where you want to be. You'd spend a lot of $$ doing that and then the intake and pushrods wouldn't fit right after. My advice is put your money into a high-stall torq converter. Trust me on this one, you do not want to run a stock converter with a low compression 440 with a cam, bottom end power will be so-so and you'll have a larger drop from idle in neutral to going into gear.