Doug, a few weeks ago, there was a question about pushrod hole size in the later heads. If you haven't had a chance to check things out, yet, here's a bit of info for you.
I have a '79, solid lifter head, with pushrod holes that measure about 9/16", that came out of a pass. car. Casting #3698447.
I also have an '82, hyd. lifter head from a full size van, that I can pass the rocker shaft thru, with about 1/16 to spare, casting #4095778. (This one's going back to the salvage yard...had some major cracks in #4 combustion chamber.)
Don't know if that'll help, but it might narrow things down a bit.

Roger

GTS225@aol.com

That's what we found, all the 80 and up hyd. lifter heads (with the wider valve cover) have the bigger pushrod holes. Good info. which has put some new thinking into the "Aftermarker" head design.
DD

I believe they used the larger pushrod holes on the hyd lifter engines so you can get the lifters out without having to remove the head.

Doug, do you still have that scan I emailed you quite some time ago?? The service bulletin telling about the 1978 Volare's with Hydraulic lifters from the factory? Maybe that could be posted here for others to reference. I thought it was interesting.
Craig


cfield@ll.net