74 blue swinger

I have a 1974 dodge dart which curently has a 318-904. I am building a 440-727 to put in. I am still looking for a rear end. I have found plenty of 8 1/4 rear ends but i dont know how strong they are or what all I will be able to do to it. I know an 8 3/4 is a strong rear end but I am having trouble finding one for an A body car. Anyone know where I can find one for a resonable price and how much can an 8 1/4 take?