302 casting on a set of 318 heads

63spf you were saying that you have a LD340 intake manifold. You will have to determine if that is the Large Port LD340 or the earlier one for the 318s with the same name LD340 with the small port runners that will work good with your 273.

You will have to figure out what you have there to make sure you get the good port match up to the 302 heads.