Depends on how often you intend to replace the fluid. Motorcraft Mercon LV is fine if you do yearly or less intervals. Amsoil Signature products generally are very good, they tend to keep the trans running cooler than stock, so maybe consider stepping up to that. Not sure about Redline trans fluid performance in the EB.
Plan to have 15 quarts handy for a fluid exchange. Maybe 20 for a multiple drain & fill. I would get the fluid exchanged the first time, then do a drain & fill every so often. Yearly if you don't push your vehicle too hard, so in 3 yrs or so, you would have exchanged the fluid in its entirety. Quarterly if you are on it all the time, so by the end of the year, the fluid has been refreshed. Or a 3x-4x D/F yearly (hard driving) / 3 yearly (moderate driving).
Mercon LV changes color quickly to a brownish red, so that is not an indicator of condition. Smell and taste, er, grit check are the main indicators in this case.