I've seen the brass synchros in the T56 and must report that they are not what you find in Muscle car transmissions...
While the overall dimension are the same, the actual friction surface is not the machined concentric knife edges normally encountered.
I did not inspect every ring so my observations technically only apply to the few rings that I did inspect.
What I did see was a conical surface with some kind of probably non-metallic lining - maybe something like you would find in a transmission clutch plate perhaps.
My immediate thought was that they had modified the rings to work with ATF.
So my question is: How does the transmission shift with 90 wt gear lube?
Also, I have seen the actual gear teeth in the T45 literally worn (eroded) away so that the tips were actually sharp!
I have never seen this in muscle car transmissions.
Of course, the teeth in the T56 are unlike any I have ever seen. First the helical angle is virtually 45 degrees and the teeth are almost half as tall and twice as many for a comparable pitch diameter in a muscle car transmission. They resemble sun gear teeth in an automatic. Again, the ATF relationship...
You might say a T56 is an Anti-Rock Crusher Muncie (M22?)