Call the shop and tell them to find the broken piece. They broke it, atleast they can find it. With this piece, it can be welded with a Ni rod, or stainless rod...
IMO
I wouldnt sweat it.You have the other two bolts to hold the engine. All of them on the other side, use the torque strap, and forget it.

[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]