Then chase the other side with a M8 x 1.25 to remove any burrs.

It looks like it will fit nicely on the right-rear stud.

I tightened it up to jam the tool on a stud, then marked it.

When I tried to break the tool loose, the whole stud turned in the vice.  The marks on the coupling nut and stud stayed in alignment.  That seemed impressive, but when I set up some tools to make sure the stud couldn't rotate, the removal tool broke loose at about 120 inch-lbs.  That's not too impressive but I suspect it should be good enough.

Thanks Mike!  I really appreciate your help!!  I need to see if I can replicate this gadget.  I'm waiting on parts and for my mechanic friend to get some time, so it may be the new year before we go for it.  Now's a good time for me to see if I can replicate your extractor!  

I was just reading your cam comparison article.  I'm amazed by your work!!

Thanks again!

Paul, the longer coupling nuts will be fine, but the stainless steel is hard to drill & tap.  I think you would be better off using regular steel coupling nuts.  The longer lengths are fine and will allow better access for your wrenches.

If I can get the coupling nuts all the way out here in the middle of the Pacific Ocean, you can certainly find some in Houston.  Try Googling "fastener supply near me".  I found a bunch in Houston.  These are just a few.

Bayou Fastener & Supply
Bayou City Bolt
Northwest Fastener
Dale Fastener Supply

I got mine from a local hardware store called City Mill.  They have a decent selection of fasteners, better than outfits like Home Depot or Lowes, but not as good as what you should have in TX given all the industry in your area.

Regarding 8mm vs 9mm.  The OEM used the 9mm studs for strength.  It was probably the largest fastener they could fit into the design, taking into consideration wall thickness of the threaded holes in the case.  The designers needed to come up with a fastener that could be safely stressed to a level that is sufficient to restrain the cylinder head during the power stroke.  The pressure is extreme and applied over a large area.  That pressure is trying to blow the head right off.  The combined force applied by the studs must exceed the force resulting from combustion pressure, and there must be a reasonable factor of safety (probably 200%).  Those studs are special.  They are a reduced-body constant-strength design with nice fillets on each end.  I'm sure they are top-grade alloy steel.  Don't nick them or chew them up in any way.  Don't grab them with vice grips, or file on them.  Note that when I grabbed the stud in my vice, I had aluminum in the jaws to keep from chewing up the stud.  

Paul, it dawned on me that you could use a 5/16-18 coupling nut.  It would work fine.  Just drill & tap one side for the M9 x 1.25 stud, and use a 5/16-18 socket head bolt for the jam bolt.  Should work just fine, and the SAE coupling nut should be a lot easier to find than the metric.