1990 C1500 Silverado no crank issue
 

I bought the truck over ten years ago and it's been my everyday driver with no problems until a month ago. I'll try not to make this to long but I want to explain what the truck is doing. I jump in my truck to go to lunch one day and it started fine like it always has, but after lunch got in truck and turned key nothing happened. Everything electrical works gauges, radio, lights etc. I messed with it turning key on and off and moving shifter back and forth for a few minutes and was getting ready to call and get somebody to pick me up and when I turned key again it fired up like nothing was wrong with it. Got back to work fine and even started it and cut it off half a dozen times and it started every time no problem. I drove it for another day or two and it cranked up like a champ but then all of a sudden the no crank issue happened again. Went through the same routine turning key on and off and moving shifter back and forth and it started again. I think this same routine happened one more time but now the truck will not crank no matter how many times and turn the key or mess with shifter. First thing I did was clean the negitive battery cable ground at the block, still no crank. I've replaced the cap and rotor button, ignition module, ignition switch, netrual safety switch, positve battery cable, battery and even replaced starter. Still nothing when I turn the key. Any info or suggestion of other things to look for or do would be a big help.
Thanks
dhall57