If its a matter of the snakes getting a good home and being well taken care of then you can make do with a 55. Are you asking how to split the tank for 2 snakes? Its a good idea to house them seperately to avoid fights and sickness being spread. Oh and eggs if it happens to be male and female.
Smaller tanks or tubs are better because they are much easier to maintain the proper temps and humidity in. Plus BP's feel more secure in smaller enclosures. But I suppose with a little work and plenty of hides you could make it work out. Something so tall wil be hard to heat. Probably 2 UTH would be needed. A ceramice heat emitter would be better than a lamp. A bedding that holds moisture good or a long flat water bowl. Like a small kitty litter pan filled only halfway. You will need to find ways to maintain the proper conditions and to keep the animals feeling safe and secure.