8 1/4 LBP Rear End in a 68 Valiant

I'm looking to put an 8 1/4 rear end in a 68 Valiant. I used to have a book that told me a cross reference and what could bolt right in to different cars. Unfortunately I am unable to find it now. Would a Volare or Aspen rear end bolt up or would the axels need cut? Does anyone have a website that tells you what parts are compatible with different Mopar?
Thanks anyone who can help me.