Anybody know anything about these heads? Prone to cracking/worth rebuilding?

First if you can, look one head over and see if the short head-bolt side is "scalloped" instead of pretty much straight except for a couple of notches..

This will tell you if it is a lightweight casting head b/c the older heavy, more crank resistant heads weren't "scalloped"..

pdq67

http://www.mortec.com/castnum.htm

Not particularly prone to cracking; not particularly worth anything

Low perf 2-barrel heads from teh early 70s

Standard 307 and 2bbl low compression 327 head. 1.72/1.50 valves and small ports. Not bad for a stock rebuild on a 307 but thats about all their good for. They are a thick casting head so they aren't crack prone. 70cc chambers I believe.