20" rims Where to buy?

[iamoscar]

I have seen some nice trucks on here with 20" rims. While I am a ways away form finishing i need to purchase the rims to make sure there are no fitment problems. When search I am finding few with the lug pattern I need and size.

I am looking for American Racing Blvd or Hopster. 20" x 8.5. All four rims no stagger.

Do I have to have them custom made or does someone stock them?

I have a 68 swb. It has a 71 disk front and new axles in the rear that are 5x5.
From what gather from the wisdom on here i need 4.5" backspace. Is this correct?

Do I need to order 5x4.75 and run adapters? I have a 5/7 drop.

Thank you for your input and advice.