If you go to this link and scroll down to page 59, you will see the different driveshafts used in 1959 trucks. Same info if you want to search it for 55.2 through 59.

http://www.gmheritagecenter.com/doc...hevrolet-Trucks/1959-Chevrolet-Truck.pdf

This confirms what Delky stated...the one piece driveshaft was used in 4 speeds only for the 3100.

You probably need the tailshaft connector and the driveshaft off a 55.2 to 59 3100 4 speed.