Serpent 960 going E powered. Need advice.

[_paralyzed_]

You simply don't need the torque a 1518 has in a car this light. Plus the low kv means you need a crazy big pinion.

The 2650, castle or tekin is your best bet and plenty of power for 100mph+ speeds.

You also mentioned future plans for a 2 speed. This topic has been beat to death. There is no advantage with multiple speeds in a brushless r/c. Just lock the high gear and run motor brakes.