Which stock head is better.......

One of the mechanics I work with has a mostly complete 79 350. He has offered it to me but I want to see if it is worth it. Are the heads more desirable than my 73's? I found a couple of threads that mention the 75-80 heads having a bigger exhaust valve. Would it be worth it to use this block and heads over my 73?

 

Ask in the small block forum.
Lots of knowledgable folks there who could give you the whole story.