F-16A/B - Block 5-20 (all PW
F-16C/D - Block 25(PW F100), 30/32, 40/42 (F-16CG/DG), 50/52, 50D/52D (F-16CJ/DJ), 60/62
X0=GE F110 engine, X2=PW F100 engine (on C/D that is).
Block 60 features, among other improvements, conformal fuel tanks, an internal targetting system, and improved avionics.
Block 50 has 29000lb engines, and improved radar, the ability to fire a wider variety of weapons (including the AIM-120), among others.
Block 50D are SEAD aircraft, taking over in the "wild weasel" role from the F-4's. Most 50's have been upgraded to 50D.