[rotorwrench]

Studs were easy to get in those days since they were a lot more common than they are now. I have the longer #8 stud in my 29 Sport Coupe's engine but I didn't use the clamp so I put one of those thick exhaust manifold washers on there last time I torqued up the head. It makes it easier to remove the distributor without pulling that nut on that stud. That particular stud location can have head gasket failures so I only want to torque it up once per head gasket change.

I looked up foundry casting marks some time ago for the 1930s era and found that there were several foundries that used a diamond shape in variations. None were exactly like it but close. Those were close enough to Detroit to have been possible suppliers. Ford only set up to cast high production engine blocks in that time frame. The model B may have been produced by Ford till the end of 1934 production but even they went in to an outsource after that. Ford pretty much outsourced all low production cast parts. They could justify keeping an assembly line for them while they were being produced for industrial power plants but I'm sure that need bled down to a minimum amount just before War Department production started so they finally shut that line down.