I have a 1975 crew cab. Iput cab & bed on to 1993 cummins extended cab 4x4 5 speed cisie.i can"t get it to start by the key put fire on brown wire start right up.i by pass neutral switch so i no thats not it.any ideas. All grounds look good.

 

Your going to have to provide a little more info as to what you did. When something is oem it's easy to troubleshoot without looking at it, but we have no idea what you have done in your swap.