Dexron II-e then Dexton III (starting in 1997) WAS the factory fill through 1998. If a driver suffered excessive NGR, there was a May 1998 TSB that covered replacement of the Dexron fluids in 1994-1998 Vipers with the new (1999-2006) factory fill Jack mentioned ( "Mopar Synthetic Manual Transmission Lubricant 75W-85"...called Castrol Syntorq 75W-85). This new fluid stayed as the factory fill through 2006. With the arrival of the TR6060 tranny in 2008-2010 Vipers, the factory fill became Mopar ATF+4.
ATF+4 has been approved to replace Dexton II-e and III.
Bottom line, if you are happy with how your tranny performs, I would suggent that you use similar fluids as to what is in the tranny now.
The "Dexrons" are RED, while the "Mopar Synthetic Manual Transmission Lubricant 75W-85" is clear when new. Take a sample through the fill hole on the left upper rear of the tranny to determine what is in it. Not all dealers stock "Mopar Synthetic Manual Transmission Lubricant 75W-85" due to it's expense.
Like Ron (who was the guy who actually tracked down retired Borg Warner employees in order to better understand the reason 92 & 93 Vipers were left out of the May 1998 TSB)...I have continued the factory fill models with no complaints or problems in all Gens of our Vipers...ATF+4 for Gen I's and our 97 Gen II...and "Mopar Synthetic Manual Transmission Lubricant 75W-85" in the 99, 01, and 03. While I have not changed the tranny fluid on the Gen IV's, I do plan to use the factory fill of Mopar ATF+4.
FINAL NOTES: Our Vipers see street use only, while some track cars use other fluids.
Also...BE CAREFUL with substitutions regardless of the claims from their manufacturers and suppliers !!! Do a search on GL-4 vs GL-5