440 source heads on a stock 440
This is ForABodiesOnly so I'm guessing we are not talking about a truck here. What are you going to use the engine for? Gear ratio? Converter? The heads will make a big difference over stock iron and the cam will make considerable horsepower over stock.
An engine does not care what vehicle it's in. Could be in a boat or a motorhome, the same principles still apply.
Think about what is being said - you want the guy to take apart his freshly-rebuilt short block to deck it 1/16" while keeping the stock low compression pistons in it. Then, put aluminum heads on. If that is the answer you want to go with, then go for it.
If it were me, I would stick with what I had for now and change the cam, it will be a more cost-effective solution until you can build a proper short block to utilize the heads to their fullest potential. It's not going to be a high rpm street bruiser. It never will be, the foundation is not good enough to support it. But, you can build it for low rpm torque and fry the tires at will if you choose the right cam for the application.
Again, a cam will not require taking the whole rotating assembly apart. Any cam company will do a custom grind for you for little or nothing over what they normally charge, they can tailor the valve events for the combo.
I've been down this road myself. If you want any real performance, the best answer is to get good pistons then build around that. Anything else is pissing in the wind.