Sorry, I cannot recommend any to you. What if after your fiance gets pregnant or the baby is here, she wants the snakes gone again because of XYZ reason? Bloods are thick and heavy in weight, not long. Nothing like a Burmese or a boa, so I don't see what she meant by getting rid of the bloods.
I have a dumerils boa and corns but I will say no more. If you had done your research on this species, just like the blood pythons, the weight/baby discussion should have been done before bringing the snakes home.
And what is your motivation to breed? There is just as much risk in breeding boas as breeding pythons.