Others may chime in, but these are getting very hard to find in usable condition. You may want to be clear you want Black color, the most more common color. And there are "deluxe" buckles with push button, and "standard" buckles (lift to release, like on a commercial airline)
I am often on the hunt for (e-body) seat belt parts on ebay. I know the part numbers, I know what they should look like. But in nearly 5 years of searching, the parts are just not there, or they're way overpriced, or they are junk and not usable.
Recently, I sought a set that looked OEM, with standard lift buckles. Not easy to find, but I found them at PG Classic and I am really pleased with the set. They look very good, pretty darn OEM. But they are missing the tiny part number swatch, but aside from this, I am very pleased. 2850-70BUK Mopar 1970 E-body Bucket Seatbelt Set