Help needed with some part numbers please

[jfnar]

I took my truck to a local mechanic to get the differential tightened up. They called and told me that they can't get some of the parts they need so they want me to get them. I really don't have time to mess with it but that's another story. It would be very helpful if someone could give me the part numbers for the spider gear, output shaft bushing, and output shaft seal or direct me to a parts list on the web. It's on a 68 gmc 12 bolt rear. Any help would be greatly appreciated.