Anyone here ever rewire an Old F2B from a 2 prong plug to a modern 3 prong?
If I'm correct the 3rd wire goes under one of the transformer mounting screws.  Just thought I'd seek any sagely advice I might get.

As I am from the UK I am assuming the third prong is the ground protection so anywhere on the metal chassis would do but then then again being a limey I could be wrong!
In the UK  unless it has the double insulation mark then all electrical items are grounded for safety as we use 240V which can be quite tingley when exposed to it!

I have performed this modification.  
I drilled a little hole near the input grommet and placed a crimp lug to the earth cable.  
The cable was then secured under a nut and bolt assembly at the hole I drilled. The paint needs to be scraped off the chassis.  
I also moved the on/off switch to the front of the device.  
I will take some pictures later.