I'm in full agreement on raising the seat and getting some backward angle. Another factor is the depth of the seat back. Even removing the gas tank will only give you more leg room if the seat back is kept low and fits into the recess.
However, in making these adjustments you have to make sure you can see out of the windshield especially if the truck has a rake because of lowering the front end.
The '99 Tahoe center seat I have in my '56 filled the bill for me.
