does size really matter?

i have had the unfortunate pleasure of piecing together rear drum brakes from scratch. 1/2 way thru the project i learn that FoMoCo had 2 different size drums and two different size shoes for the same application. i have called several Mustang shops in the area and not a single person can tell me what the difference in 10"x1 3/4" and 10"x2" drum brakes are......well, besides the obvious 1/4". also, does anyone out there know if the backing plates are the same size? The application for this mess is a 68 coupe with a 302 and an 8" rear-end.
thanks in advance.
 
different plates

I did this conversion on my 66. I had 10x1 3/4" and put on 10x2" using Aerostar drums and 67 Fairlane wagon backing plates. If you go with the 2' wide setup you will need the backing plates for it. There's a link somewhere on the conversion and it mentions using the Aerostar plates as well. Not sure if that'll work, I think the bolt pattern is different :shrug: .

Ken