I quit shortening drive shafts long ago. Go to the wreckers with a tape measure, you'll find one that'll fit.
Done a few of these swaps. Place the engine as far back as possible, to the point of having to beat the flange on the firewall flat and denting the heater housing for clearance. Cut a notch in the X-member for starter clearance, and use the "soup can" starter. Notch the frame for fuel pump clearance. This way you can use the common long snout water pump and factory alt and PS mounts, and the balance of the truck is much better.