The stock shaft should be 1310, we only like that joint to 500HP in a drag race application. It is important to know the length of the shaft and the top RPM of the shaft. That can be closely estimated by engine RPM in the 1:1 gear going through the traps.
The information necessary can be found at pstds.com in Driveshaft 101. Please feel free to call with any questions 727-442-1711. We ship in a couple of days.