Help! 360/4-speed conversion in crisis!

Hello, I recently inherited a 1970 Plymouth Duster that was in the middle of a conversion from a slant 6/automatic to a 360/4-speed. The 360 is a LA block. The engine and transmission are in place and much of the work so far has been forensic. My dad was a capable mechanic but this particular project had been shelved about 10 years before I got my hands on it. I was installing a new starter so I could begin putting on headers and exhaust. While doing so I noticed one of the bolt tabs attaching the block and bell housing had snapped off during installation. Upon further investigation I actually found the tab itself in the many boxes of random parts that came with the car. I’m a sheet metal worker by trade and a pretty decent tig welder. I know how difficult a job welding this tab back on can be. Question is: is that my only option in an attempt to repair this issue? Is it even worth a go with how finicky cast iron can be? How common is this issue when attaching a transmission? Most resources I’ve seen that have addressed this have been on aluminum blocks and bell housing. It’s getting harder to find a built LA short block and starting from scratch would be very expensive. What can I do from here?