Adding Bronze Bushings to Ductile Iron Rockers

I don't know what guys are making their rockers out of.

But ductile iron has yield strength around 40000 psi.
7075 aluminum is 55000 psi+
Now if it's being made from 6061, that's much weaker than iron.

40ksi is a min, but it can be specified as high as 90ksi. No clue what grade Chrysler used though.