won't start

A timing chain issue is a possibility on your 2004 Chevrolet Silverado 1500 but not likely. You could start by looking for moisture in the distributor cap, if that looks ok then check timing chain slack while you have the cap off.

ck for spark ck for fuel pressure with a gage

I'm betting my life that its the crankshaft sensor make sure to by a good quality part.Theres a TSB about that issue sensor is giving ECM a 50 degree advance timing reading.