You could do what I did and forego that tiny circlular emblem and buy the nice 3 inch enamaled PCA badge. The decal fades faster then the badge by the way! I attached it to my rear engine deck intake grill (left side) and it looks great. If you opt for the decal, the drivers side rear window corner has always been the spot I am familiar with.
Bob
1973.5T
PCA member