8.75 A body U joints?

My 66 Dart has a 6 and had the 7 1/4,pulled that and put in 8 3/4 .489.The driveshaft I used was from Donar car(73 Swinger 318 auto with 7 1./4)I used a 7290 u-joint in the rear and it bolted right in(no shortening)So I would say you need the 7260 u-joint.I could be wrong,if so someone will correct me!