Fair asking price for a 904?

I already planned on a suregrip either an 8.75" or 8.25" (if I can't get the 8.75"). I was told from the get-go the 7.25" would turn to butter behind a V8, and that they were worthless too. I also had either a T56 or Passon 855 in mind. That's why I was asking about what the slant and 904 would go for. As it stands, at best they'd sit in the garage for years to come, and only get used if I do a 3rd build (if I were to do a 2nd build it'd be a 77-78 Power Wagon, twin turbo 318 w/ a518 auto).