I couldn't even put a number down. I would suggest that you pick what types you want, get say ~10ish of each see how things turn out. You will have fry live to adulthood so you don't need to fully stock the tank. But of course some of the fry will be hybrids, but some wont, and with that sized tank it will look very cool with a lot of mbuna swimming around. Just watch water parameters and all should be good.
(Remember we like to pack in more mbuna in are tank to keep aggression checked, you have the space so the real question I think will be how many fish the filtration system can handle and that isn't something you will know till you try it out.)