[R-390] R-390 Grounding Question

[rbaldwin14]

I just got my first R-390 (Non A) and it came without a power plug.  I was successful at getting one and now want to wire it up, of course.  

It is plain to see that the AC lines go to pins A & D and it looks like the ground can go to pin C.  Does that sound correct?  I've heard something about not having the third wire in the supply line so having to ground separately, i.e. my question.

Do the line filters in these boxes leak like the A's do?  I run my A's through an isolation transformer.

Thanks in advance for your council!

Rich Baldwin
KD6VK
Durham, NC