While some people say that oil pan is what to use on an A-Body because it has the indentation, it doesn't really work (as you have found out).

Both the 187 and the 699 oil pan have the indentation too far forward (close to the sump area).
They simply don't clear, I've got a factory 69 383 GTS and tried both the 187 and 699 oil pans when I was mocking up everything in the engine compartment for clearance and neither one cleared the center link at the idler arm.
The recess is in the wrong spot to clear.

I ended up using a 7 quart Hemi pan that I recessed my self with a hammer and a larger socket to make clearance.
I looked to see if I had a pic of the recess that I added, but none of the engine pics show that part of the oil pan.

Both the 187 and 699 oil pans are actually listed as C-Body oil pans.
http://www.440source.com/oilpans.htm