Going to check out two Red Tails...

[xFenrir]

How true! I just adore Peaches' eyes. My favorite feature.

Beautiful pic! She looks good. When are you going to go see her?

I'm about to leave as I type this.

If you only want one tank to clean, then I would suggest putting the BP into the rack and the boa into the tank.
Boas need more room than BP's do. I follow the general rule of about 1 square foot of floor space per 1 foot of snake length. For smaller boas, tubs make great "grow out" enclosures until they are big enough for more permanent enclosures. You can even go with a VE-175 tub from ReptileTubs.com, which has about the same floor space as a 4 X 2 enclosure.
For a 3 year old boa, I would suggest a 10-14 day feeding schedule.
Boas aren't technically "arboreal", but they are very adept at climbing, and will often use anything extra that you give them to perch on, whether it is a branch, wood poles, or just laying on top of their hides.

I'm also thinking of that too. I want to get into breeding Balls, so I was going to make a rack system sometime anyway, so now would be probably the best time to make the switch huh? I've got her in a 40 gal, though, that wouldn't be too small for a RT? I've read they need about 6 feet of floor space, or something like 46-something long (I forget the dimensions). I'm worried she wouldn't have enough room.

Definitely visit the shelter before making any final decisions; boas are very different from ball pythons handling-wise; though the majority of boas are completely docile (excluding nippy hatchlings), they are not jumpy or nervous in the least like ball pythons are. Both of my boas are very relaxed and calm, and definitely enjoy being out.

Another big difference between boas and ball pythons is feeding. Boas are aggressive feeders, and that is often times connected with cage aggression. Both of my boas are complete sweethearts to handle, but are extremely cage aggressive. Hook training is absolutely vital if you want to avoid bites (and big boas can pack serious bites! I've had my hand pretty badly torn up by a female that was just 4ft!).

Also, due to their great feeding responses, obesity is often an issue with boas. Don't overfeed!!! For an adult/subadult, a meal every 2-3 weeks is plenty of food.

Good luck! She looks gorgeous, I'm sure you'll love her! My boas are among my favorite snakes, they are excellent pets!

We're going today to check her out, and then we have to go through the adpotion process so we'll have time to go and get all her necessities (I've got most of them already, but the main thing is getting her an enclosure). Thank you so much for the tips, I've read up on them seriously, but it's always great to get handler experience.