Chances are you will need to scarf off your old spring mounts and weld on a new set. Speedway has them cheap in there catolog. Just get out your tape mesure and go to town. Measure center to center on your springs. Then Wheel mounting surface to WMS. Then WMS to center of spring hanger. if the measure from WMS to center spring is to short on your new RR don't use it. The tires mite rub. In this case a little more is better. I don't know if you can hook a newer drive line to the older type tranny. Ask around if that is what you propose.
