big block head castings

So I have a question that maybe someone can verify for me. I have a 66 383 that has head castings of 2406518 I recently head that this was the worst head that Mopar ever made that I should think of upgrading to a 2780915. Has anyone else heard of such a thing. I have new springs, valve seals on them averaging about 110PSI on compression. It has new cam, lifters, push rods, timing set. nothing was done to the lower end at all other then the looked at to make sure the bearings were still ok.