1965 was the first year for the slip yolk on an auto trans. Manual still had ball & trunnion in 65.
You are fine as long as the driveshaft angles are correct. Hemi drag cars back in the day made more torque and power and the B & T driveshafts were fine.
Everything is stock so the angles should be fine. I threw on a kit from Brewer’s.
One word of caution on the B&T. Make sure you don’t over grease the unit on a drag car. I have seen a few boots burst from grease settling in the boot over time then at very high speeds - 120 +, the centrifugal force rips the boot. This was back in the late 60’s, maybe the new boots are thicker.
