Leaf spring bushings

hi fellow mopar brothers I have a 1970 duster with a 7 1/4 and I'm changing it to a 8 1/4 rearend I bought it off a guy on Craigslist it's complete including the leaf springs and I want to get new leaf spring bushings and i want to know the size or are they the same as a 7 1/4? The 8 1/4 came out of a 73 duster 4 speed 318 car the rear end has 3 21 gears non posi