who runs 13sec to 12.80 in the 1/4

Moper,
You forgot to add in the cost of the rocker arms and the lifters and pushrods for the magnums.
Also another thing is the velocity that the heads will have will be different and what the engine can use and or need will be different, so what rpm you want to turn and where the engine will be driven at mostly will also be a determining factor as to which heads would be used. Another thing is that if you only have a .480 lift cam and you have peak flow at .550 or .580 from the heads then the smaller heads that peak flow at a lesser lift with a smaller port, and flow similar to the larger port at low lifts will be the better choice. The port velocity will be better and the throttle response will be better along with fuel mileage for the street. This way the smaller valve head would be better than that of the larger valve head. Not saying the 302's but the small valve 360 head.