OK neutral safety circuit. Look at your starter relay mounted on the firewall. You have two "push on" flag terminals, they are the relay coil. One wire goes to the bulkhead connector, and supplies the "start" signal from the ignition switch to the relay. The other terminal leads down to the center pin of your neutral safety switch. That switch must be grounded to allow the relay to engage, and is supposed to in park or neutral.
So make SURE the vehicle is out of gear, and remove the wire going down the firewall to the transmission. Jumper that flag terminal to ground. Try the key. If it does not crank, put a light/ meter on each wire (the push on/ flag) and look for power with the key in "start." If you have power and it won't crank, check out the start relay
Also try jumpering the two largest exposed starter relay terminals. It should crank, and this shows the wiring from there to the starter, and the starter itself is OK
