wtb: Driveshaft for 65 dart 273 4sp 8.75 trunion
I believe that you need to shorten a 7 1/4 driveshaft about 2" to make it fit with an 8 3/4". We usually took them to a driveline shop to have shortened and balanced.
From 904 to 727 also needs to take out another approx 2". I don't know about 4 speeds.