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

Thanks. What condition for that kind of money?
Use the search function and look through old ads. You will see what kind of parts are available and for what price. Because it's a big piece you may want to check out car shows and/or swap meets in your area. Freight to ship a rear end across the country could be a deal breaker.