Rear drum backing plates

Someone please talk to me about these. I've got a 1993 nova and the backing plates from what I can see so far have rusted away in places, pretty much un-usable . But I've looked at different models and my back plates have an outer lip that wraps around the outer side of the drum but others I've seen the outer lip tucks inside the drum.
Was there a change at a particular age model?
It seems to be a better design idea if there tucked in as it stops the rot but is it easy enough to convert to this set up? I assume the shoes maybe different so I guess cables may me different too?

I have a set for sale if you need replacements

I have seen yours but what model/age nova were they from?

http://i1050.photobucket.com/albums/...pspd5uxcaj.jpg
http://i1050.photobucket.com/albums/...pssjirco0n.jpg
http://i1050.photobucket.com/albums/...psboqnrlmh.jpg
http://i1050.photobucket.com/albums/...ps3mjy9hmv.jpg

So this is what I mean. I can now see the back plates tuck into the drum and it wraps around the outside. I've removed the rusty outer edge so would be useable if everything can be removed but sadly the axle has a snapped bolt in the shock mount and there's s patch of rot that I cannot get to without taking it apart so looks like I need to save what I can and get a bare axle to build it back up.


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