Why does my 1984 nissan 300zx cut off while driving down the road?

Why would it have a switch? Fuel cut off switches are found on race cars. The closest thing you probably have is a fuel pump relay. As for the location of that, this thread is good: http://forums.nicoclub.com/1984-300zx-fuel-pump-relay-location-t567634.html

YOU WILL HAVE TO CHECK THE ECU FOR ANY CODES FOR STARTERS.

You should not have to take axle out to replace studs.

Sounds like an electrical problem, make sure the ground leads to the engine are good and the battery terminals are clean. It might just be a bad connection in the wiring harness try jiggling the connections to see if it makes the gauges jump when it is running.

SOUNDS LIKE AIR FLOW METER, CHECK CODES

It is attached to top of intake where throttle cables are attached to.

ck your maf sensor. The first sensor out of the air cleaner. It controls Air/ fuel ratio. Good Luck, Ned

Chane the plugs and HT leads.

the timing belt should be changed every 60,000 miles.
your engine is an interference engine, which means if the timing belt breaks or skips, the valves will hit the pistons.
if your belt broke you will have bent valves. so the heads will need to come off and bent valves replaced.

it is adjusted by the idle screw on the aac valve located on the plenum