Yes and no.
The late Type III and all Type IV models have a half-cock notch and inertia firing pin. All US Armament Corp has done is deepen the half-cock notch a bit and add a heavier firing pin spring. The latter is a simple call to Wolff. The former, I would bet you could fit the US Armament Co. hammer if you could get one. Otherwise, fitting a later Type IV hammer, firing pin, and firing pin spring is (supposedly) possible for all models.