there are four species altus,falactus and two yellowtailed varieties red tail (altus and falactus) are smaller than yellowtail two or three small ones can be kept in a 55 but 75gallons up is usually better
I'd say it's better to stay away from most predatory characins in a 55. Predatory characins tend to be claustrophobic and skittish. A red/rainbow wolf might be okay and a chalceus might last you a while, but that is probably all you will be able to come across that would fit in a 55.
There are 12 known species of Cachorros (Ace. Family) however the term Red Tail Cuda or Freshwater Barracuda is used liberally through out the hobby as common names for a whole bunch of different fish Acestrohyncus Falcatus the "Red Tail Cacharro" would greatly appreciate tank lengths of 5' long or more and at least 1.5' wide. 55 gal. is a good Exodon Shoal tank however you'd need to check your state invassive species list to see exactly what toothed Characins are legal in Florida.
No sadly I've already barked up that tree, I pray for the day I move to Tennessee and I can keep all the fish I've dreamed of... Lol but seriously I hate our laws.
I've found any of the "barracudas" to be skittish and didn't have any luck getting them off of live which ultimately becomes expensive and potentially hazardous to the 'cudas with the chance of introducing diseases.