I watched a neat webinar on eTorque yesterday during lunch. The BSG integrates a PCM and inverter module.
Personally, I'd yank the inverter/HPCM out and just drive the phases with a VESC 75/300 or an openinverter.
Ran some simple calculations and the 5.7 HEMI BSG could theoretically pull ~275 amps, likely just in short bursts such as when spooling up the main engine. Even 200A continuous would likely let the smoke out.