Intake manifold/ timing/

1991 mustand gt 5.0 302 ford five speed manual trans. I changed out my valve cover gasckets. And intake gaskets as well. I removed the distributor in the process. I marked it in place thus to put it back in the same place. Everything was put back in order even the dissconected gas line rails. The car will not start. It just pops and cranks over. I looked at everything twice I even cleaned the intake completly before putting it back on. I put my distributor back in the same locatin as well. This car had never given me any problems at all it just idols and crancks a lot. I checked the fuel line and presure its ok.