Re: 1972 shift switch
I can't think of anythig that would cause the scenario you describe,other than a bad switch. Is is a new one or used?
But here are the facts: There are three basic look-alike switches. All three will fit in the control.
Electramatic, three wire
Hydro-Electric, three wire
Hydro-Electric, five wire
Electramatic just flat won't work, so you can't use that one.
hydro 3 wire will work, but you won't have start-in-neutral protection. To make it othrwise work, connect the two white wires together. But be careful, it will then start in gear.
hydro 5 wire provides start in neutral protection.
Use a voltmeter to diagnose the problem.
There should be 12 volts at the purple wires in any gear (key on)
There should be NO voltage on either green or blue wires in forward gear.
There should be voltage at the green wire in neutral gear.
There should be voltage on BOTH green and blue wires in reverse gear.
EDIT: 3-wire switch (1971) is part number 384042; 5-wire switch (1972) is part number 385253. Expect to pay $300 - $400 for a new one---IF you can even find one. They're going fast.