Rescued red tail boa and dumerils boa

Hi I just recently got a 6 foot red tail and a baby dumerils from a friend never had boas before the red tails cage is too small for him so I ordered a 75g will that be good for the rest of his life? Also I was wondering if a 4x2x1 will be big enough for the dumerils when he is full grown?

Congratulations, those are both amazing snakes to keep.
I would go for a 4x2x1 for each. Of course you can make a 75 gallon tank work for the boa no problem, but I’ve found keeping heat and humidity in tanks that size can be difficult. It’s very much not impossible tho.
I think your 4x2x1 should be good for your dumerils boa too. Really depends on how large he gets but I kept roughy a 6.5ft male in an almost exact same enclosure and had no issues.
Good luck with your new snakes, and I think you’ll find boas to be very awesome pets.