Question about tank filler neck for 69 camaro
 

I need to get a profile shot of a stainless replacement tank for my 69 Camaro tank. See the attached photos from my mock up with a GM OEM style tank. Since I'm running a 4 link and the rear leaf spring mount in the frame rails will not be used, I'm going to run a 1-1/2 inch tube through those mounting holes for added rigidity in the rear. I am already replacing the floor pan, and the pan is going to be trimmed and massaged, so I will be modifying the pan too.

While mocking up the tank relative to the tube location I noticed that the 1-1/2" tube will clear the fuel tank braces that are welded to the trunk floor/tail panel, I just need to notch the top of the brace. The only interference I can see is the tank filler neck. As you can see from the photos of the stock tank contacts the 1-1/4" thin walled conduit that is being used for mock up prior to welding in the 1-1/2" tube.

Will a replacement tank do the same thing? Is the filler neck in exactly the same location? Does anybody have any experience putting in a tube at that location and having interference there? Anybody have a good contact at Rick's or Tanks Inc or Rock Valley that can give me good dimensions?