There is no true ajustment for thrust on a Sixty crank. You control thrust by the placement of main bearings as you mention in your post. I have never found an actual specification of thrust for the Sixty. When I started mine was approxmately .250"- which was way, way too much.
Not quite sure of you reference to # 3 and # 4? The only way to control thrust is by placement of the mains.
uhhhhh yeah I meant the rear of #2 thrust and the front Of #3 thrust.Paul