I've thought about a left hand drill bit. If it were long enough to reach that might be good solution. I don't know what ARP is, but I have a local Fastenal store. I also think when I replace it I might use a heavy duty washer under it, just to make sure it isn't bottoming out.

I assume that it would require careful cleaning of the hole once I got it out. I don't think any of the head bolts go through into water or oil passages in this engine (1960 235).

Tim

I am currently digging back in to a 1953 3800 (one ton) with a nine foot bed. I've owned it since 1979, and drove it until 1982 (or so). My wife got me involved in restoring it back in 2002, got the body removed and the frame redone, then things came up. Now I am retired and starting again. If anyone is interested I have photos on Imagur ( https://timwhiteblues.imgur.com/ ). I live way back in the woods in the Ozarks on 40 acres at the end of a 2 1/2 mile private road.

Tim