Motorcycle Repair: rear wheel bearing replacement 1978 xlh, rear wheel bearings, wheel bearing replacement

Question
1978 Harley XLH -
Question 1 - Are the rear wheel bearings and seals available at an auto parts dealer? I need to replace mine and I was told they are the same used in some automobile wheel bearings. Timken comes to mind, but before I tear into it, what are the bearing and seal numbers? The Harley dealer does not carry them here locally and said I need to take them apart first to get the numbers. It would be nice to have them in my hand before I take the back apart.
Question 2 - Sitting on the bike, how tight should the chain be for correct adjustment?
Thanks  

Answer
I dont know if the wheel bearings can be purchaced or are the same at auto parts stores, since I dont have any kind of cross reference for that. You can purchace them at any aftermarket parts company by mail if your local harley dealer doesnt have them, however. They should be able to look up the numbers for you in their parts book. Here are the numbers if you want to order them.
Seal: 47519-72
Bearing: 9052
For the chain, you should have around 3/4 of an inch play in the chain
Good luck and happy riding
Mike