60's and early 70's had the thicker tubs on the Dana's, after that, they thinned up. I use the 489, tapered rear end in my 69' 340 Swinger, 4 speed, that is a little stronger than the other two 8 3/4's. Remember, using the truck or van Dana's, you also need to get rid of the 8 bolt safety axles and install the 5 bolts. I believe the Dana's without the center 8 bolts are the thin ones. These rears (truck and vans) also will fit the "B" bodies. Only a half inch difference. The spring blocks need to be moved, if I remember correctly.