You did not say which engine, so just go here http://autorepair.about.com/library/firing_orders/bl-Chevrolet-firing-93.htm and choose the correct engine.
Need to check or replace the ingnition module in the Distributor.
0.060 inches
I believe it is 45
4.3? Follow the spark plug wires from the spark plugs, they will lead you right to the distributor.
What i would do first is check the distributor cap and rotary button that's what usually goes bad first. if that's not it it could be the coil or maybe even the distributor itself.
What is spark plug's position? tell me.
Is it a brand new distributor ? If not then replace the module and pick-up coil in the distributor that you have.
see if the coil is sparking to the distributor cap
electronic spark timing is your distributor.
Check the module under the distributor cap.
The ESC module is in the distributor
Bad coil Distributor cap Rotor