Bought a 70 Dart Custom Parts car and I have a question.

[j061093409]

4 door cars have different front and rear GLASS which means that the roof is not a direct replacement.

 

[BigWhi]

Where do you see four doors?

 

[Jimacuda]

Looks like a 8 1/4 to me. Looking in a little phone screen though. Nothing wrong with a 8 1/4. Much better then a 7 1/4. Would be big bolt too

Yup, 8-1/4 would have to be big bolt pattern. They did not come in small bolt pattern.
73-76 rear most likely.