Radio, physical differences?

[Kalums]

I've been on and off the internet searching for an answer to this question for 3 days.. (I swear the internet gods hate me) I've got an opportunity to purchase a used Autosound custom USA-630 for under $100. I was wondering if there is a physical difference between a 1971 GMC radio "3 hole" set up and a 1973 3 hole... The one I'm looking at seems to be the same as my 71 with just a different bezel behind the 2 knobs... Any help would be greatly appreciated