Converter drive tube cracked
 

I just bought a TCI streetfighter for a th 350 for $80. It looks good and all the standard checks like stator clutch operation and endplay turn out ok. Fluid is a little dark with no metal.
Problem is the barely visible cracks by the corners of the tabs on the pump drive tube.
They are about 1/8" long. What causes this? Can a regular converter shop replace just the tube and will the whole converter need disassembly? Can the cracks be tig welded and smoothed? Thanks for any advice.
Does anyone think this was an ok deal?