You may need to drill either the block or the heads (or both) so that the coolant ports on the newer heads match the older block. The ports on the intake side are slightly different on the newer heads.
if you use an aftermarket intake you won't have to worry about the water passages. you should be able to use either set of pushrods, just make sure to check the rocker geometry.
I recently put a set of GT-40 heads on my 289. I think the early 302 is the same. On the newer heads, the water passages between the heads and the block changed (on mine anyway). I had to drill the heads to match the block. I also had to use 6.905" push rods for my flat tappet lifters.