While it is commonplace for a side valve Briggs to break its connecting rod, it is nearly always for one of three reasons:
1. Engine run without oil.
2. Engine run with governor disabled, resulting in gross overspeed.
3. Engine incorrectly assembled.
The state of the crankpin is the most likely issue as to whether the crankshaft can be saved. So far as the rest of the engine is concerned, my recollection is that it is an early Chongqing Briggs with a broken connecting rod. There seems little point in regarding it as anything but scrap aluminium. And I don't know what the broken piece is, in that sixth picture.
