These load modules were made especially for this project, but can be used for amp testing too, for sure. Each resistor has the rated power of 50W, so, 8pcs = 400W.
Guys, I am developing devices, I am not a filmmaker
I found just one pic from the testing process. As I remember - right before the load was connected.
On the scope - signals of 400/12V module PWM; signals of synchronous rectifier's.