Enclosure size

I have a 66 gallon(40x20x20 inches) enclosure free. I'd really like to get a ball python, but I'm unsure whether this is too small or if it'd work.

Thoughts? Thanks! :)

Size-wise it should be fine. I would replace the screen top with one made of plexi to keep heat and humidity inside.

That's a huge tank for a Ball and would work fine. Mines been in a 40 her entire life with me. If you get a young Ball you will need to add plenty of stuff to give the snake a sense of security. Things like hides, plants, driftwood, etc.

66 gal is plenty for an adult ball python! If you're getting a juvenile, I'd recommend something much smaller to start with as the snake could feel too exposed in such a large environment. Something like a 25 gal should be fine, but if you only have access to the 66, be sure to add lots of places for the snake to hide.