Driveshaft compatibility questions

Hi,I have a 68 Dart with 7 1/4" rear and torquflite. I'm going to convert it to an 8 3/4" abody rear from a 71/72 car. My question is would there be a difference in drivershaft length between a duster/demon abody and a dart hardtop or 4dr sedan? I know that 8 3/4" rears used a smaller driveshaft but would the length be the same for Dusters and Darts? Thanks