Sounds to me that he did not heat the parent material correctly, didnt get it hot enough before welding. Id say he just chased the crack to the end of the bellhousing.

72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72. Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.