The 8L is a pretty high kv motor, considering that most go with something in the range of an 1800-2200kv motor for truck applications. the 20T may be a bit too much. Try a 16 or 18 pinion. The 145-160 range is ok, but it will go up with extended runtimes. Going with an external bec and reducing the gearing will help with the temps on the esc.