Seat help and question

I m my 74 duster i m changing the bench seat to a bucket seat. I have the tracks and i have the bucket seats. 2 questions. I know about the fact that you need the 4x4 or wat ever they are little steel plates i can make those but my question is how many do i need? do i need one for each hole so 8 total? or do i need only 4 and put them in the back 2 holes? question number 2. Do i need to use different seat belts or will the orginal bucket seats belts work.
Thanks