I thought all Pontiac 400 heads had pushrod guideplates. I see none on your heads. I'd say this might be your problem.

In your lower pic, you can see a small portion of the hole where one of the guideplate hold down bolts is supposed to go.

And, the rockers shouldn't contact the spring retainers. As far as I know, all stock 1.5 ratio Pontiac 400 rockers are the same. I've swapped rockers from 350's, 400's, & 455's. Never noticed any difference, & never had any hit the retainers. I have seen the valve tips worn down to the point where the rockers were almost touching the retainers.

Don't have any pics of #14 heads. But below is a pic of some #11 heads. It clearly shows the guideplates bolted into place. The 2nd pic, of some 7J2 heads, shows exactly where the hold down bolts are located.