What do you call large growing? And large in mass, or length?
If you want to see Endemic species, have a look for the Buccochromis Heterotaenia(the largest/heaviest) cichlid from lake Malawi. Rhampochromis and tyrannochromis species get large and long too. The Fossorochromis Rostratus can get quite large too.
All these species are from lake Malawi, the other lakes I don't have as much knowledge of. Don't expect these species to get as large as your emperor cichlids from tanganjika
The Serranochromis Robustus gets pretty large too, but is not endemic.