Won't be that simple. The THC300 uses a "sensor card" (the 9 pin card at the plasma) that has a voltage divider/filter on it along with the input pins t fire the torch and get the OK to MOVE back from the plasma. You cannot simply hook to the divided voltage on the Everlast and use that and you can't use their Raw Arc volts output pins to feed the SENSOR card inputs because their raw volts is high impedance (100K series resistors) and the SENSOR card is low impedence and will load the circuit. (high tech way of saying to won't work)
Some of the later SENSOR cards for the THC300 had an input for divided volts (50:1) so 5 volts = 355V at the torch. That will probabaly prove to be in accurate since it is an analog voltage that has to travel all the way back to the THC300 main module and ANY noise over about 5o mvolts (.050 volts) will skew your readings and settings.
The electronics "language" difference is the basic language barrier between Chinese and US technical people. The concepts are the same but the names of things are different and the way the electronics are implemented are different.
Even the 12 pin connector is not a standand connector used in the US or the EU. The only place you can get the 12 pin round plug to match their connector is from them or a source in China.