Tri-Y headers have been around for a long time.
They were used on small blocks and less on big blocks.
The pitch was the same then as it is now - tri-y had smaller tubes and gave the benefit of increasing low end power - a good thing for the small block.
The merge collector exhausts used larger tubes and had higher flow rates. Result was more power at the top end with a lot of air moving but a bit less power in the mid range than a smaller tube tri-y.
You might conclude that for stock Viper with those small block holes that a tri-y has a benefit in the mid over a merge. But that the merge will flow more air at the high rpm use or forced air conditions.
They were used on small blocks and less on big blocks.
The pitch was the same then as it is now - tri-y had smaller tubes and gave the benefit of increasing low end power - a good thing for the small block.
The merge collector exhausts used larger tubes and had higher flow rates. Result was more power at the top end with a lot of air moving but a bit less power in the mid range than a smaller tube tri-y.
You might conclude that for stock Viper with those small block holes that a tri-y has a benefit in the mid over a merge. But that the merge will flow more air at the high rpm use or forced air conditions.