That is the right tail shaft from e-bay and the short shaft pictured is correct but you can see it also is not phased correctly. Cross member looks good. Look and see if the top of the cross member to frame rail is shimmed down. I see a gap and most likely the guy who worked on it was trying to correct the angle due to vibration. As said best to replace the tail housing and shaft along with the correct short shaft. Bolt the cross member solid and you should be good to go. Question with the truck in park and you increase the rpm's is there any vibration? Just making sure the converter in correct balance wise to the motor. That would be just one more problem the builder could of caused.