How much interchangeability is there from all the various motors, from the early 5.7 all the way through the Hellcat motor?
My personal interst is if the rockers and shafts, etc of the 2006 5.7 I have will work on Apache heads? What about swapping other parts around from all the different motors??

My understanding is that all rockers are the same.
They are of the same ratio and dimensions.
Early heads to 2008 5.7 have shorter valves. Everything else is the same length but different dia.

Rockers are all the same.

Here's a brief, but good OEM head comparison write-up. The valvetrain is briefly described for each.

http://www.hotrod.com/articles/ccrp-1210-inside-the-g3-hemi-cylinder-head/

Ok, sounds like the pieces that hold the rocker sfafts would be slightly different? With making the valves in newer heads longer, it would seem logical.