Will a Viper T56 bolt up to a Gen3 Hemi 6.4?

Uh, no...
That thread is full of misinformation that I won't even get into here- suffice it to say as far as the GIII Hemi and the Viper V10 are concerned, there is no interchange of bellhousings or flywheels. I've had them both (bells and f.wheels) and went down that rabbit hole years ago with my first Hemi swap, based on bad information I was given at the time. And fwiw, the truck V10 doesn't use the same pattern as either the Viper or the G3/LA/Magnum; it uses the same pattern as the Cummins, which uses an SAE pattern, I forget offhand which one...