10 inch backing plates

While I don't agree the improvement is "minimal", I certainly wouldn't go out
buying parts just to make it happen either. Since you have both setups in your
possession, you might want to go out w/the tape measure and check the knuckles
to see,if they are not compatible then you have nothing.
A member was selling 10" A knuckles awhile back, but as some disc conversions
are using them,that's where I would go if I would bother to buy them. Also,the B-
drums are 4.5"BP so...,were you planning on changing bolt patterns as well?
Again,even if you could use the knuckle-LBJ-drum-brakes, you would have to get
'73 and up upper arms to use them. Which means buying parts to get it done.