That tank is plenty big enough for Africans. It's longer than a 55 and the same depth so the height really isn't gonna pose a big problem.
I've got probably 40 Africans in a 55g with a Fluval 305 canister filter on it. Obviously none of them are adults but overstocking with juvenile fish in an African tank will make aggression basically zero out.
I've got yellow labs with white labs, exochromis, venustus, electric blue ahli, all types of mbuna's, pheno's, obliquidens, nyererei, etc etc etc
If you live in an area with good LFS that accept trades and such I would advise overstocking it with juvies until u decide which u like the best. Then I would trade the others in. As adults you'll have to tone it down to maybe 4 or possibly 6 depending on the type/size of Africans you choose.
If you don't have the option of overstocking and then dumbing it down later on I would probably say you have room for 4 adults as long as they aren't haps or one of the bigger Africans such as Frontosa.
Hope that helps. And if you care to see how overstocked my 55 is, www.youtube.com/sirreal303
check out the most recent video. It's in there.