Bm:

Since you are in the fortunate position of shortening the aft section of the front shaft, it may be done by you thus:

1) Remove a portion of the aft section to create a new section of the correct length, making sure that the cut ends are square.
2) Have a machine shop turn a piece of tubing ~3" long so that the tubing is a light press fit into the cut pieces of the shaft. The splice tubing should have a finished wall thickness of ~.080-.090".
3) Drill two holes of 7/16-1/2" in each piece of the shaft about 1" from the cut ends. These holes are for plug welds.
4) Press the splice tube into one of the shaft sections 1 1/2" and tack weld one of the plugs. Press the splice into the second shaft section, and finish weld all the plugs & the butt weld between sections.
5) Send the whole driveline to Portland for balancing, and, if necessary, replacement of the u-joint.