I am doing the same exact thing to my '65 Barracuda. The 8 1/4 shock plates are 3" just like the 8 3/4. I was lucky enough to find some through FABO, actually got mine for free from cosgig. Just ahve to look around, check any local yards or Pull-a-Parts, lots of vehicles had 8 1/4 or 8 3/4. I found a Volare wagon at my Pull-a-Part that had an 8 1/4 but when I went back they had crushed it already. Good Luck!