Decode Space Saver Wheel/Tire - 1971 Trans Am

[bgolz]

Could someone please decode this wheel for me?

I need a space-saver spare for my 1971 Trans Am, and all the codes are pretty confusing.

Here are the stampings for what I am looking at: K 3 9 - 5 (stem) 7 UA

I know the "K" is Kelsey Hayes. Is the "3" the plant code? Is the "9" for 1969 or 1979?

What year is the UA code for?

What broadly would be correct for a 1971 Trans Am..both space saver spare size and wheel stampings?

Thank you.