1996 chevy WT 1500, cranks but won't start

It is probably the magneto or it isnt getting to mag

There is no magneto on your vehicle, however, you may have a bad ignition coil or the ignition control module needs to be replaced, these generally go out after a couple hundred thousand miles due to extended periods of heat causing the coil case to crack & lose it's coolant oil, and similar problem with the ignition control module, these have a heat sink and rely on dielectric grease to help keep unit cool. Try using a spark tester with a fully charged battery, and check for spark at each spark plug connection. If no spark try replacing coil first, less expensive, ignition module is a little more cost to replace.