First off, that is a WAY to big enclosure! The absolute max any BP should be kept in is a 40 gallon breeder tank which is 36 by either 16 or 18 by either 16 or 18. Second, the best way to heat a tank is a heating pad and a ceramic heat emitter(CHE). As long as you get an appropriate wattage, you don't actually need to regulate the CHE, but you absolutely must regulate the heating pad. To regulate it you can do 1 of 2 things
1. Buy a rhetostat
These are only about 10 dollars and basically dim the unit, cooling it by an amount you control. You cannot set it to stay at a temperature. Instead, you check it several times a day and adjust accordingly. This is what I do because I am cyber schooled and can check it pretty much whenever I want.
2. Buy a thermostat
This is much more expensive, but you don't really have to check on it.
If you do get one of these, do not get one with a temp drop. This is not necessary or desirable.

Basically, if you are home most of the day or could check it every 2-3 hours, get a rhetostat and save about 100 bucks.