Vented vs non vented gas tank behind the seat.

[chewychevy67]

I have a 67 and I am keeping my tank behind the seat. I remember in my old 67 that when the tank was full when you turned left I would always get a little spillage down the side of the cap on the paint and then would smell like gas. If I go to a 71 72 non vented tank does this still happen? What do I have to do to make this work correctly in my 67? Any info out there? Thanks in advance. Rod.