G506 - 235 cu. in motor

[BrianC]

I am restoring this engine as close to original condition as I can. I am about 95% complete and was getting ready to install the oil dip stick and tube when I think Bubba bit me again.
This engine has the extended oil pan and a photo I took when it was being dismantled showed a bracket from the dip stick tube to an oil pan bolt. I determined that this was incorrect and started a search to see if I could find a correct period image, locating one in TM9-765. This shows the bracket attaching the tube to the block about 2 in. above the pan. The only spot on the block that looked correct was where the dip stick originally entered the engine before it was modified for the military. I assumed that this opening had been factory sealed. I became convinced that this was where the bracket should be attached to the block and started to scrape away paint and pry off the cap. What I was able to pry off was a 3/8" round head rivet that was probably held in place with Lock Tite. The remains of threads were visible in this hole, so I think that the tube for the dipstick was attached here with a bolt.
The first problem is how can I restore the threads without getting debris into my engine. The second problem is I don't think the dip stick tube is correct because there is no way the bracket on the oil pan will clamp the tube tight. Does anyone have an extra tip stick and tube?

BrianC.