Have a 1995 chevy blazer 4.3. Started by producing a p0300 code (random misfire). Started replacing parts 1 at a time with no change. Spark plugs, plug wires, distributor cap, rotor, catalytic converter, plenum gasket, intake manifold gasket. After I changed the intake manifold gasket I didn't set the timing right so the engine backfired. Reset the timing and the engine would not crank. Found a leaking fuel line inside the plenum and replaced it but engine still will not crank. I don't know where to look now.