I've gradually repllaced all the ships in the game anyway. Everything in the Fed , Gorn, Hydran, Lyran, most of the Romulans and most of the Klingon fleet is actually wrong, model wise!! But luckily nice and talented folks have provided all the correct replacement models in places like Battle Clinic.
The model quality of rth ereplacements is far better than the orginals too.
For the Feds the ships should be as follows:
FF = Burke Class
DD = Saladin Class
NCL = Kearsarge Class
CA = Constitution Class
CB = Achinar Class (Connstitution Class will do)
CC = Constitution Class
BCF/BCG = Belknap Class
DN = Federation Class
BB = Federation Class
Klingon ship are self explanitory as are the Gorns, Hydrans, Romulans, Lyrans and Orions.