Are gravity fed fuel tanks legal in Texas

I hope this is the right place to post this and if not I apologize in advance if I'm wasting anyone's time!

 

I recently purchased a 275 gallon gravity dispensing tank on a stand at auction. It was a great deal.  I've grinded off the rust and repainted it and now it looks amazing.   My question is are these still legal to fill in Texas?  I'm trying to decide if I just paint the block ATM on it and use it as yard art, or paint the block ATM on it and make it functional .

 

I can call the county ext agent or the local fuel supplier but they are always trying to sell me something.  

Are gravity fed fuel tanks legal in Texas