Where did you guys find your 8 3/4's?

Man I had no idea how hard these things are getting to find! My car came with an 8 3/4 as it's an original 340 car. I did , however manage to kill my 4.30 third member an I was shocked to find that used ones are going for $500.00! I replaced the 4.30s with 3.55s and did the big bolt patern/super stock springs and B body 10 inch shoes(wider than a body). The only way to do it is to bite the bullet and loosen the wallet.