YOu can swap the heads, with out changing anything other than the intake manifold gaskets. Just bolting on the heads won't be much of a gain though. What are your overall performance objectives? Lots of folks here have built motors, and learned many learning curves!
great upgrade, I did it to my 289 about a year ago. I could really feel the power on the freeway. Just make sure you get them rebuilt. you dont have to change anything, its a straight bolt on to your engine
I swapped them onto my buddies 68 but I think he had a roller block because it didnt have the clutch zbar hole in the side of the block. I would imagine that you would have to check the pushrod difference if any. I have some gt40 pushrods if you ever need to compare em I'll send you one.