As a certified welder by trade- I would not touch it. A few reasons:
A) balance will be off.
B) if cast - weld cracks after the weld and that piece letting loose at 5000rpm would be like a bullet. 50/50 chance though.... centerline down hits the ground centerline up its all leg. Liability is crazy.
C) bolt loose up. After welding you need to retap threads cause they will be off. Could cause issues.
D) what you will spend on welding it properly with no guaranty, your possible in the replacement crank range.
Not worth the energy - make it a display item. Tell people it came from a motor that set a world record and not worry every time it runs “will today be the day.”
Just my humble 33 years as a professional welder opinion.
