I have a quiz this morning, so I can't take the time to go into detail now, but I will ask a few questions:

How old is the snake you're getting?? Unless you're getting a breeding size adult, I suggest sticking that 40 in the closet for now and getting a 10gal tank or a 12-15qt tub instead. BPs, unlike most other reptiles, do NOT need a lot of space especially as little ones.

Do you have the most important item: The Thermostat? No matter what size or type of enclosure or heat source, you NEED a thermostat to keep the temperatures stable. Rheostats and dimmers only work when your room temps stay within 1 degree all the time.

When I get home from Chem. today () I'll go into a bit more detail and send you my Tank Setup Tips, if you like.