7260 big enough???

As I usually lean on the side of caution, a 1350 wouldn't be bad idea, especially with a 4-speed. But my solid Spicer 7260 joints have lasted several years with wheels-up launches and the car weighing around 3,540 and has been as heavy as 3,720 for the next slower class. I've never added grease to it. I went with a steel billet rear end yoke because over time, the ears can spread and the u-joint will hammer out. Driveshaft is custom made from better material. Basically, given enough time and "hammering", the weak link in the drivetrain "chain" will show itself.

People have gotten by with less without issues. But the extra insurance can reduce worries. I'd actually like to switch to a Dana 60 if I can ever afford it. It lasted for many years of racing twice a week in a lighter 10 second Challenger I had. But I had lots 8 3/4" parts for my current car and swapping gears (center sections) is so easy. The ring & pinion is now my "weak link" and I check it periodically.