Ok lets go back to the basics for a minute. Check all your fuses first. If all is well there I think it is time to test the ignition switch on the bottom of the column. There should be a purple wire comming out of the switch harness that goes to the neutral saftey switch (pretty sure that year was still purple). See if you have power at that wire with the switch in the start position. IF no then there is a problem in the switch or with voltage getting to the switch (if all gauges and accessories are working and check eng light is on then you have power going to the switch). If yes then go to the neutral safety switch and check power in and out. If you have no power in (with switch in start position) then the wire between the switch and NSS has a break in it. If you have voltage in but not out the the switch is bad or off adjustment. If you have power in and out but still no power to the starter then you are loosing your power at the bulkhead connector or there is a break in the wire between the bulkhead connector and the starter.
The bulkhead connector has been known to corrode and create either a voltage drop or no voltage at all. If you think this is your problem then disconect the battery,unscrew the center bolt on the engine side of the firewall bulkhead connector, clean the connections real good, and put some dielectric grease on the connections and put it back together and try it again.