Axle Swap to upgrade to a 4.5" BP

I have a 70 Duster 340 4 speed with a 8 3/4" rear end. I want to got to a 4.5" bolt pattern so I'm looking to swap out my axle shafts. Is there another A Body model (or B,E, etc body) that I can take the axles from. For example, the 73 Duster has a 4.5" BP, will those axles fit in my rear end without modification? Questions concern length, strength, spline count, etc. Thx