Is there a mat or cushion between the fuel tank and body?

A few years ago I replaced the OE fuel tank in the 68 Barracuda with a new tank from Tanks Inc. Over the next few days I am going to be working around the fuel tank to improve the accuracy of the fuel level sender and I was wondering, per the title of this post. Does the topside of the tank fit firm against the underbody, or was there a mat between the two?
I have a vague memory of having something between the tank and body, but not sure.
And if there was something between the tank and body, what was the mat made of, source for a new one? Any issues if I just leave it out? Or should I loosen the straps and move the tank down enough to slide something in there?
thanks