After rebuilding the transmission, it will not shift out of first gear?

I would start by checking fuse # 9 and 14 in the junction fuse box on the inside of the truck, and fuses # 1 and 3 in the fuse panel under the hood. There is also a transmission control relay in the same fuse panel under the hood I would swap out. If these are okay or don't fix the problem, I would say you got a defective rebuilt valve body and transmission solenoid assembly. Here is a guide to help check the fuses and the transmission wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please let us know what happens.

Yep, you can put 12 volts to the shift solenoids to see if they click and remove the shuttle valve to see if they move freely and make sure the check balls are in the correct placements. Also, it is important to tighten the valve body evenly.

Valve Body to Case Bolt 100 in. Lb
Solenoid Wiring Connector Screw 35 in. Lb
Solenoid To Transfer Plate Screw 35 in. Lb

CAUTION: Do not force valves or plugs into place during reassembly. If the valve body bores, valves and plugs are free of distortion or burrs, the valve body components should all slide into place easily. In addition, do not overtighten the transfer plate and valve body screws during reassembly. Overtightening can distort the housings resulting in valve sticking, cross leakage and unsatisfactory operation. Tighten valve body screws to recommended torque only.

Here are the instructions on how the valve body is assembled and it shows where the check balls go. Check out the images (below). Please let us know what happens.