rc,

   Last time my ole '91 Astro did that it was the ignition module inside
the distributor.  If it's got a carb like mine, one easy way to check it
would be to remove the dog house and top of the air cleaner and pour a SMALL
amount of gas directly in the carb... if it lights, then it's a fuel issue,
if not, probably the ignition module.

Good Luck

You need to verify:

1) Fuel delivery
2) Spark delivery
3) Ignition timing (if #2 is ok)
4) Engine timing/compression

It's one of those 4.  Figure out which then we can take it from there!

Doc