Like Paul said, any corse splined yoke will fit the tranny, but there were a couple of different u-joints used depending on the application.
55-57 car and 55-59 std. 3spd 1/2 ton trucks used the same driveshaft assemblies. These were 54 7/8" overall length (minus the yoke). The GM part number for the yoke on these shafts is 3707059. The HD 3spd and 4 spd 1/2 tons had a larger u-joint, but will still fit the tranny.
If you can't find what you need over there, I'm sure somebody here can cut off the ends from one of these driveshafts and mail them to you. Then you could have a shop over there make/balance a new driveshaft.
