Have a 1951 super A. Runs good and all and have been changing fluids. Last item is draining the hyd. res. and removing the screen. But the fill plug is a square 9/16 head steel plug. Its seized up and not moving. Ive tried every tool I can think of and am messing it up. Ive heard of a tool for them but not sure it would go on it. Its directly under left side of gas tank so I cant heat it safely without removing it. Any ideas? Which would help more heat or cold? Thought about freezing with freon. Then won't have to deal with gas. Ive seen normal drain type plugs on other ones and will get a new plug to replace.