On my -6A, I followed the -7A preview plans for the firewall forward placement of most items. The gascolator ends up on the front side of the firewall, lower RHS. I had to make a secure standoff for the gascolator so the drain plug would clear the lower horizontal motor mount tube.
I used a longer drain fitting so that it would just come flush with the bottom surface of the cowling (this determined the vertical mounting dimension for the gascolator). A small hole in the cowling allows access to the fuel drain fitting for taking a fuel sample.
Why did I go to all this trouble? In my mental analysis of possible failure scenarios, I envisioned the AC sliding along the ground after shearing off the nose gear and leg. I did not want the gascolator fuel drain being the low point that would next get sheared off and allow the contents of the gascolator to escape.