so I've scrapped the idea of using 11 inchers on the rear of my Val (thanks for the heads-up). But are the backing plates for early 10 inch rear small bolt brakes the same as those for the big bolt pattern variety? I have the proper resplined axels and bbp drums; is it now just a matter of putting the proper shoes on or will I need later plates as well? thanks again for any help!

No, the small bolt axles have 1.75" width brake shoes and the big bolt axles use a 2.50" width brake shoe. The backing space is wrong and will not match up correctly. On the otherhand the 10x2.5" backing plates are interchangable with all the axles that used that size of brake shoe.