Changing oil in a 742 differential.

68 Dart GTS with a 742 differential. I'm changing out the leaking pinion seal and want to drain all of the 50+ year old oil at the same time. There is a plug on the side of the carrier @ about the centerline of the pinion. I assume this it the fill port. Some oil drained out when I pulled the seal, how do I remove the remainder? To refill, should I go with the Chrysler oil and friction modifier (have the P/Ns), or is there something off the shelf that is just as good? And last, can someone confirm what the pinion nut torque is? Think it is 230 or 240 ft. lbs. Thanks in advance.