1997 Chevy Silverado timing

I have a 5.7 vortec and I changed the head gaskets and put it all back the same way and I put one 1 piston up and the mark on the harmonic balancer lined up with the mark on the timing chain cover and put the distributor where its suppose to be lined up and every time I try and crank it dont start so I put the mark on the harmonis balancer back with the marks lined back up and the rotor button on the distributor ends up 180 out every time even if I correct it