A piece of my engine block fell off

I agree 100%.
The idea that this will fall off with improper welding just does not fly...It's bolted on...it does nothing but seal oil at this point. Seal it up good (you're choice of method), bolt it down. It will be fine...you're holding nothing up with it.

 

I may be trading a AX5 tranny I have laying around for a running 258. If the trade happens I'll probably just put my current engine to the side and worry about it later.

I appreciate all the help.

 

that can easily be fixed by a machine shop. When i had my l head rebuilt it had a crack from a valve seat all the way down the cylender wall. Getting a new block would be very stupid