Rear Axle Help

[mvfd70]

Well I surprised myself today. I'm rebuilding a 72 5 lug rear end to put under my 68. The surprise was that I got it apart without breaking anything that wasn't already broke and without loosing any parts. I've never worked on a rear end before so this is all new. Glad I got a shop manual for the truck. Anywhoo...I've got two questions about it so far. First, can the pinion gear shaft be separated from the pinion gear or is it one piece? The pinion bearing evidently went bad and tore up the shaft. I've got another rear end that I can harvest parts from but the gear ration is not the same. I haven't counted the teeth on that pinion yet to see if its different. If it's the same then that wont matter. Second, does anyone sell the rear drum brake dust covers that go on the inside of the drum? The plate that holds all the drum brake hardware and that the brake cylinder is attached to. Thanks in advance for your help.