Need help to identify 727 trans

All 727s that have a slip yoke are long tailshaft. This is the setup that you want for a car. If you use a short trans with the fixed yoke you will need some sort of slip joint (on trucks and motorhomes this is at the center driveshaft hanger) to allow for the loading and unloading of the rear suspension. I have never heard that the short tailshaft is stronger. Virtually all car and drag race applications of 727s use a long tail shaft and slip yoke.