The tire track eel will grow the length of that tank so no. Peacock eels are nice and all but I could never get mine to eat. The gar might make a tastey snack out of it so no.
A 3 foot tank is no place for that gar. Or a 12 inch fish for that matter. The only 12 inch fish i would keep in a 3 foot tank would be smaller bichirs and smaller eels.
If you ditch the gouramis and the gar, i'd suggest get another senagal bicher or even a Delhizi. Another fish i would look into are Leopard Ctempomas. You can find them in any petsmart and they only get 8 inches tops. For mid water swimmers you could stock larger rainbowfish, congo tetras, angels, and/or smaller cichlids like Acaras, Convicts, Jewels, Firemouths, or Festivems.