32 tudor gas tank mounting

Does the gas tank on a 32 tudor go on top of the frame rail or does the gas tank lip go under the frame rail ? I have seen both and wondering which is correct
Thanks

 

It goes above. There are two bolts that fasten it to the left rail, and one bolt with a spring and castle nut that fasten in to the right rail.

 

Everyone I've seen was mounted on top of the frame rail.

 

Top of the rails. HRP