Hi, I notice a difference in the design of the rockers and brackets between older heads and "newer" 4A heads.
Is it possible to take the whole rocker setup from an 4A head and bolt it on a #7 head or a B head?

 

#7 yes
A and #2 heads are 1965 issue, and they use a single year only different rocker setup with studs that have I believe 3/8" thread into the heads. All other heads 1966+ [B-Ka and #3-on] should be able to use the same rockers.

 

so even though the setup looks different between #7 and 4A, they should interchange?
I am not sure what they are called, girdles maybe? the bracket-thing that holds both rockers down with two bolts are different on the 4A head than on the #7 head.

 

Keep in mind if you mill the heads a lot, your lifter preload will be too tight with factory length pushrods. Just mentioning it, goes with your other thread.

 

It's called a bridge and there are two designs, the three-piece design (two die cast trunnions with a stamped sheet metal bridge) and the one-piece design (trunnions and bridge in one die-cast piece). As Chris noted, other than the 1965-unique parts that fit the 3/8" studs, all are interchangeable.

 

ahh a bridge, thanks :-)
Okay, which is the 4A design then?

 

Should be the one-piece die cast design.

 

ok. Thanks!