Well, the Cheetah D (and E) would be the easiest to make. Just add some bits to the vertical fin and raid the Kfir and Mirage 5 COAM parts bin for the rest. Well, the two seater would also need a new ventral er... fin/fuel tank thingy with a redesigned rear part.
The Cheetah C would require more work : new IFR probe, new canards, lengthened front fuselage, new radar nose that could maybe be reused on the Kfir C10/CE... The oy specific part already done is the frameless windshield.