The heads and cams are identical. The difference is the weight of the Cobra's forged internals. If the Mach is stick, only the crank is forged. If it's an automatic, none of the internals are forged. The non-forged internals are cast and are much tighter and lighter, reducing the amount of power lost in just moving those parts. The Mach's engine is identical to a stock Marauder's engine, so I have some experience
If I have two identical Marauders, one with a stock engine and one with a forged engine (otherwise exactly the same), the forged engine will be 20-30hp less, guaranteed. The benefit is though, the forged engine can take a lot more abuse and make more power at the end of the day.