I agree with Heath. Why take a chance on one or both of the new additions being bullied or worse?
A pair of occs came with the used tank I started with. I didn't know what I didn't know at that time. So I bought a beautiful pair of black clowns to add to my 75g tank. By then, there were at least 4 btas in the tank to share. But the blacks were immediately picked on by the established occs pair. I read up on it and found that 2 pairs of clowns, especially 2 pairs in that size tank, had very little chance of getting along. (They are damsels, after all! Lol) So I gave them back before something ugly happened.
No regrets, the fish in my tank all get along. That's my goal.....