I have yet to see the tip go wrong, "From front side look at the bottom two center retaining nuts, if a socket cannot access them to remove, only a wrench, then it is a 9”
I think all galaxies had 9 inches up to the mid 60s when a GM type was used for ones with small motors,my 64 custom with a six had a 9 inch. Jeff
[addsig]
I think others have described the shape of the 9" looking at it from the rear of the car as rounded all around. The 8" is flatish on the top and on the bottom. A little like a pumpkin.