Need an 8 3/4 for my 69 Dart 413/727, help?

5 x 4.5 for sure, front is already done, everything new w/discs. I want one ready to install depending on condition. I have other repairs/upgrades that can't be funded if I spend it all on the rear end. I need to do some research on the site. Thought I looked at both those sites already but will look again. The 4K+ mention by me was for all new. thx