Define "difference".

Early (87/88 ish) F3 electrics are called "pre-PGM" and are similar to early RS in that the CDI and RC valves control boxes are seperate. They cannot be plugged into a normal NSR setup unless you have the entire CDI/RC box/coils/adjustable stator (which requires the F3 cases and crank) etc.

Later F3 stuff was PGM-II and the PGM looks exactly the same as a mk-II mc18 or a 91/92 RS. It even plugs in and works on a normal mc18 mk-II loom (as does the RS PGM) but you need the engine work for it to make better (or even the same) power.
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