I've been looking and am getting conflicting results. It's a given that the '64 only narrow case HEH-D used a 4-11/16" front bearing retainer, '65 and newer went to 4-7/8". What I am trying to determine is whether '63 and older T-10's used a 4-7/8" major diameter retainer as well as the '65 and ups, making the '64 bell the only year set up for the smaller diameter. Looking to figure this out for trans and bell compatibility. Input appreciated- Len