[John R]

Anyone here know if the 6000A meter will work in the 600A? Looks like it, exc for the transistor test part at the bottom.

Unfortunately, No.   Check free downloads on the following: http://www.stevenjohnson.com/hickok/data.htm
The 600A meter movement is 233 ohm, 500 uamp. Hickok 66G, Pt. # 660-005.
The 6000A meter movement is 1165 ohm, 100 uamp. Hickok 66K, Pt. #660-125.
Do a search for Hickok parts as I saw somewhere, can't remember where, that someone was selling Hickok meters/parts- but was not cheap of course.