1967 Dart differential question

Look at the axle cover, if it has six sides its a 7.25, if it is an oval shape it's a 8.25. You could have either the 7.25 or 8.25 in large bolt pattern. Also NO A-body prior to 1973 models came with the large bolt pattern of 5x4.5(5x114.3) they came with the small bolt pattern of 5x4.
The 7.25 is worthless and just junk it, however if it's a limited slip/suregrip (or Posi in GM terms) it is worth a little bit. Just know that a stock slant 6 can break them so don't expect much. The 8.25 is a much stronger axle and has great swap potential. You can easily get pre-97 jeep Cherokee rear disc and limited slip units and put them in the A-body rears and it will a mildly built V8 without a problem.
The 7.25 and 8.25 are the most common found under A-bodies however you might get super lucky and find the big daddy of them all, the Dana 60. That would be worth the most by far either cut down to a body specs or worth a S*++load more if it's an original 68 hemi barracuda/68 Hemi dart rear end.