I don’t know why you wouldn’t just go out and try the stall test.
It’s free, easy, only takes a few minutes, and would give you valuable info.........for having a phone conversation with a converter shop, or just for knowledge about the overall combo.

Not to mention, if the converter flashes way less than 5000, then that dyno sheet becomes even more puzzling.

Edit: I went to the TA site...... looks like their 518 converters are 10”.

I would expect a motor combo like yours to flash a tight TA 10” to around 4000-4200 doing the high gear test.