When I was a kid I had one escape it's enclosure and live in my room for about a year. Most reptiles would seek a quite place away from people but not my Tokay. He lived right around my aquariums/cages (they were warm) for year and bit me at least 5 times in that year in attmepts to get food that I had in my hand.
He was an impressive ambush preditor... too bad I felt like I was his prey!
Males are very intolerant of each other...
Tokays can get a foot long (a little more for males, little less for females) so I would suggest a 4' tank as a minimum as a life long enclosure for an adult pair. a 55 would work though a 75 or even a DIY 4' x 2' would be better.
A 40 breeder would be okay for a young pair that has not yet reached full adult size.