Switching rear end to lbp

Hi,

I am a MOPAR newbie and I am sure this question has been answered before,
but i have a stock 69 barracuda with 4 wheel drums and 8.75 rear. I have an opportunity to strip a disk brake setup from a 73 340 duster. Since this setup will have 4.5 inch bolt circle (and assuming rotors are useable), can I just yank the axles out of the rear of the donor car and use them in my 69 rear end so that I am LBP all the way around? Also, if rotors are trash, will 72 and earlier rotor fit on the spindle so that I can maintain the SBP all the way around?

thanks