Modified Alternator bracket snapped mid rev
355 LT1.
I have seen regular stock brackets crack from built motors when those rear braces were removed (usually because of headers).
used the stock short one attaching to center rear of alt to the forward head exhaust bolt hole (not used with headers). Just bought a spacer to mimic the stock exhaust manifold set up
The one that goes to the #4 exhaust port bolt (need longer header bolt) came with my headers to replace the stock one that went there.
You could fab up something similar for rear accessory bracket bracing







