LBJ difference between 69 and 70 for Disc

I would like to put a set of Kelsey Hayes discs on my 69 Dart--I bought a complete setup with LBJ from a 70 Duster---I have read some articles where they say that 69 used a different size than 70 ---I have also read where they instruct you to just redrill the size of the bolt hole on the existing LBJ from 10" drums.

Any input would be greatly appreciated