1996
350,5.7

After putting everything back together after replacing the intake manifold gasket the engine is very hard to crank but every once in a while (4 or 5 start attempts)
it starts perfectly and runs great, but if I turn it off it goes through the same thing again hard cranking.

Is it possible the rotor or distributor is on backwards? (I changed the rotor and am pretty sure I put distrubutor back in same spot but just trying to think of what it might be or would it not start at all if this was the problem.
Would a crankshaft position sensor cause this behavior? I don't have andy code testers but would go get one if this would help diagnose.
I am trying to narrow down the possiblilities before taking it in for a diagnosis.

Any suggestions would be great

Gary

BUY A NEW TRUCK, ITS THAT SIMPLE