Unless your GM charger has a constant current/constant voltage mode I would not use it. If you use a LiPo pack on an appropriate charger it is very safe. If you don't you basically have a small firebomb...i'm not kidding!
If you are running LiPo in an RC car be sure you know what the max current your motor/gear ratio combo will pull. A sedan with a 19T motor will see 50 amp+ spikes if you bump a wall under power. You would need a 2s3p pack of 10C 2100Mah cells (7.40v 6300Mah) to safely handle that. FYI, that pack would run a car for ~10-12 minutes at a race pace