Well, a 180 ft one would be Gargantuan (or maybe even Colossal), but I'm not sure there's enough else to it other than just a nonstandard advancement for the dire eel. And the 180ft version just seems like an advanced version in the original text anyway. I'd lean toward skipping unless you think it's different enough.
How about we just say it's a Stormwrack Eel with the Mystaran Gargantuan template?:
Super Eel [A Stormwrack Eel with the Mystaran Gargantuan Template]
Gargantuan Animal (Aquatic)
Hit Dice: 16d8+112 (184 hp)
Initiative: +5
Speed: Swim 60 ft. (12 squares)
Armor Class: 18 (-4 size, +2 Dex, +10 natural), touch 8, flat-footed 16
Base Attack/Grapple: +12/+37
Attack: Bite +21 melee (3d6+19/19-20)
Full Attack: Bite +21 melee (3d6+19/19-20)
Space/Reach: 20 ft./15 ft.
Special Attacks: Attach, swallow whole
Special Qualities: Low-light vision, scent
Saves: Fort +17, Ref +11, Will +6
Abilities: Str 37, Dex 13, Con 24, Int 1, Wis 12, Cha 2
Skills: Hide +8 (+12 in coral or rock), Listen +5, Move Silently +3, Spot +6, Swim +21
Feats: Alertness, Improved Critical (bite), Improved Initiative, Power Attack, Skill Focus (Hide), Stealthy, Weapon Finesse (B)
Environment: Warm aquatic
Organization: Solitary
Challenge Rating: 7
Treasure: None
Alignment: Always neutral
Advancement: 17–40 HD (Gargantuan)
Level Adjustment: —
A typical super eel is between 50 and 75 feet long and weighs about 8000 pounds, they can reach 180 feet in length and weight up to 100 tons.
COMBAT
Super eels are generally shy and only attack if disturbed or surprised. They can strike with startling speed.
Attach (Ex): If a super eel hits with its bite attack, it uses its powerful jaws to latch onto the opponent’s body and automatically deals bite damage each round it remains attached. An attached eel loses its Dexterity bonus to AC and has an AC of 16.
An attached eel can be struck with a weapon or grappled itself. To remove an attached eel through grappling, the opponent must achieve a pin against the creature.
Swallow Whole (Ex): A super eel can swallow opponents up to three size smaller than itself by making a successful grapple check. Once inside, an opponent takes crushing damage equal to the creature's bite attack plus 8 points of acid damage from the creature's gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the gizzard (AC 15). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A Gargantuan super eel's interior can hold 2 Medium opponents, 8 Small opponents, and 32 Tiny or smaller opponents.
Skills: Eels have a +4 racial bonus on Hide checks, which improves to +8 in areas of coral, rock, or heavy kelp. An eel has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.