Physically I'm pretty sure it'll be a straight swap, but you will face some electrical issues.
While the F1 has a permanent magnet 1-phase alternator with a combined regulator/rectifier the B1 (77) runs a 3-phase excited field alternator with a separate (electromechanical) regulator and rectifier - this setup is unique to the 77 models (B1 and C1) and later model reg/rec's will not work with the 77 alternator. This is not just a question of 1-phase vs. 3-phase, the 77 runs a field coil and later model reg/recs do not have an output to feed the field coil, completely different animals.
This leaves you with two options, provided you still have the F1 engine:
1: Install the 77 engine, get hold of a 77 regulator and a 77 rectifier and modify your harness.
2: Swap your F1 rotor/flywheel, stator and stator cover onto the 77 engine and use the F1 reg/rec, no mods to the harness required. This may take some slight modification (drilling) of the F1 stator cover as the 77 models may have the cover dowel pins located differently from later models.
Personally I would prefer the latter or better yet (third option), stick a 750 or GPz 750 engine in it if you can find one.
77 KZ 650 B1, 82 GPz 1100 B2.
