If you want to know the actual current going through the motor under load, you'll need either a dyno with some current measuring gear (eg: https://www.rctech.net/forum/radio-e...-master-7.html) or a data logger in the vehicle when you drive it around. Some, not all, ESCs have some data logging built in, so check the specs/manual/etc of whatever ESC you have on hand. Eagle Tree used to sell a data logging suite, but they're no longer around.


OT: 12AWG wire is often only recommended for 25-30A (just do some internet searching) There is a huuuuuge YMMV when it comes to this (aka caveats and considerations, eg: sexy multicore wire is less current capable than solid copper, and brushless motors are not inherently "continuous current" devices).

FWIW: Hobbywing used to publish some basic data, but again, a number of assumptions went into that. For example, an XeRun V10 G3-3.5T was rated for a maximum power of 462W and current of 126A. The latter for more than a short period (seconds, most likely) would result in the stator windings melting. (ref: https://hobbywing.com/en/products/xerun-v10-g327.html)