"Looks like you need to do the entire rad support, not just the top piece." that's correct---the radiator support consists of the upper panel, the headlight mounting panels and the lower splash pan. I did a similar swap using an '83 front into an '86 body. In my case I wanted to keep the original lower pan so I separated the upper and headlight panels (drilled out spot welds) and mounted them to the later lower panel (pop rivets).
To my eye the less protruding nose of the later hood looks better than the earlier one--a modified grille would be the way I'd go -- but in my case the newer hood was bent and the grille smashed. -- Dave