It depends on friction losses in the drive train.
A power glide is generally about 18%. Most 3 speeds are 20%. Sticks are slightly less than a PG as a general rule.
So the 580 with a PG would be 690ish.
I was looking at Boosted’s numbers and his converter is so loose you can’t get a pull on it.
On my dyno I try to get the pulls 8-10 seconds long. You get more data that way, but it skews the numbers a bit higher doing that.
We built a dyno car at the last shop I worked at. We bought adapters for every engine as they came through the shop.
We had a PG and a very tight converter so we could load the engine long enough to get good, useable data.
I doubt Boosted’s engine is actually making peak torque at 5700 rpm. He is way short on cam to get peak torque that high.
The only way to know for sure is to get it on a crank dyno and see what you get.