Yes, I'm glad you pointed out that the stock manifold already does this.Well for a typical 4 cylinder with a firing order of 1,3,4,2:
2 and 3 would be paired
1 and 4 would be paired
Each pair would join and feed a separate side of the twin scroll.
For the 7M to be paired into 2 separate inlets for a twin scroll:
With a firing order of 1,5,3,6,2,4:
1,2,3 would be paired
4,5,6 would be paired
The stock exhaust manifold already achieves this, it has a center divider pairing off the 2 sides...
Though the CT26 turbine housing does not mate up with an equivalent twin scroll design. (At least the Supra CT26)
There is a CT26 turbo for another vehicle out there that did utilize an early twin scroll turbine design though.
The 3SGTE engine received this style turbo.
Though the passages are too small to be suited for the amount of airflow needed on a 3.0L engine.
Perhaps someone here who was CNC skills can recreate this ebay unit, or we can use the one I've linked below. I think this would make an affordable, cast, T-4, and twin-scroll manifold setup without paying an arm and a leg or having to do extensive custom work.