In a pinch, I just used a 4lb dead blow hammer on the handle of the breaker bar and whacked it damn tight.

The tool, no pictures version. Get a piece of 3/16 or 1/4" steel bar maybe 1.25-1.5" wide. Figure out how long to cut the angle piece by holding the bar with centerline on one of the holding holes in the pulley. Measure with a tape a length such that when the cutoff piece is bolted to the remaining long piece, the hole to the crank bolt is unobstructed. Measure to the far side of the long bar so you get enough length for fastening. Cut off the piece. In the long remaining bar (henceforth the handle), mark and punch a spot 1/2" from the end and one side, and drill the hole to take a bolt the size of the holding holes in the crank pulley. Install a bolt with a protrusion length equal to the depth of the holding hole plus the thickness of the retaing nut/washer, and install said nut/bolt/washer. Drill the stacked cut off piece and handle, with the cut off piece (the yoke) held in the same position as where you measuree it's length to in the first step, and install a pivot bolt and retaining nut. Hold the handle and yoke in place and mark the hole for the second holding pin on the end of the yoke piece, 1/2" from the inner edge. Install a like protruding nut/washer/bolt, and the crank holding tool is complete. I recommend sizing the handle so that it will rest on the frame rail a la the starter crankbolt removal method. Despite reported failures, I still like that one. The unfortunate just didn't hold their mouths right...