DJ! is more or less right, but maybe the numbers differ slightly in New Zealand.
FC are the 1986-1992 RX-7's, also called 2nd generation RX-7's. They all have the 13b engine.
They are divided into:
Series 4 (S4, 1986-88) with 146 hp@6500 rpm 138 ft lb @3500 rpm
Series 5 (S5, 1989-92) with 160 hp@7000rpm 140 ft lb@4000 rpm
Both series had single turbo versions, called the Turbo II. S4 with 182hp/183 ft lb and S5 with 200hp/196 ft lb.
The FD, is the 3rd generation of RX-7's. They are all twin-turbo 13b's. They have 255 hp and 216 ft lb.