fourperf,
You may wish to consider dye penetrant as a viable alternative to "magnaflux". However, cracks in Norton crankshafts are rare. And should they develop, catastrophic failure is soon to follow. So, if your crank is one piece, chances are it has no cracks.
Notably, reputable sources recommended that you replace all the studs and nuts on your crankshaft, as long as it’s out of the engine.
Jason