Joe,
If you go with screw-in stud rockers, you can get AMC-specific 3/8 or 7/16 studs from WSC in GA. www.classicone.com ... in the AMC section. They are made by ARP. I spoke with Ron Waters yesterday about them. He's very helpful. They're made to simply screw in on the 1970 heads, no machining what so ever is required. Later heads need the typical milling of the embosses and taped for 7/16-14 threads for the stud. Also, Ron said the 1970 heads are fine without guide plates.
Aluminum rockers would be fine for the truck engine ... that's what I'm going to run on mine.