caging

Question
what size cage can I house an adult male Nicaraguan boa and a female dumeril's boa in/

Answer
Well, either of those snakes get roughly 6-7 feet in length as adults, so I'd look for something 4'x2'x18" or so.  Vision Cages makes some exactly that size and they are WONDERFUL cages.  Plus they stack on top of each other, so, since you need two of them, that will save you a lot or room.  I'd try to find a reptile show near where you live which they would be attending so that you can save on shipping or see if perhaps you can find some used ones.  They last forever.