3/32"
An Allen screw is not likely in that period Pontiac. Try 15 mm regular wrench.
Usually a 1/8 Allen key
7mm Allen wrench
There is no Allen wrench, I believe it is 14 mm open wrench.
9mm Allen wrench
3/8 inch Allen wrench.
You need 3/8 Allen key.
it is a 6mm allen wrench. A ball type allen works best to get to the plug.
I believe it's 17 mm wrench, not Allen key.
You need a 3/8 Allen Wrench
It is not Allen . It is a 14 mm open wrench
Most likely a 15mm wrench. Unlikely to be Allen in that vehicle.