318 Head Opinions
You said this would be a rarely driven street car and once in a while 1/4 mile car. I think the choice is dependant on how serious you want to get. I think that both heads would have great street manners. From previous posts with BJR and several others I tend to lean towards the magnum heads for performance. The 302 casting has just as much potential but, probably would take alot more machining than the magnums just to get to the bolt on performance of the magnums. If initial cost is not an issue I would go with the magnums. You can find magnum valve train parts at most salvage yards too. Of course matching your components is just as important.
Also, If your going this far you should really think hard about going the extra step and swapping to some higher compression pistons. The 318 stock pistons sit way...... down in the hole.