Although carrion crawlers are now "product identity", I still think its OK to use one for a sample creature. (Besides, it'll never come off the unconverted list otherwise!)
Applying it to a carrion crawler...
Mystaran Gargantua Carrion Crawler
Gargantuan Aberration
Hit Dice: 24d8+192 (300 hp)
Initiative: +2
Speed: 60 ft. (12 squares), climb 30 ft.
Armor Class: 22 (-4 size, +2 Dex, +18 natural), touch 8, flat-footed 20
Base Attack/Grapple: +18/+44
Attack: Tentacle +40 melee (1d4+7 plus paralysis)
Full Attack: 8 tentacles +40 melee (1d4+7 plus paralysis) and bite +35 melee (3d6+7)
Space/Reach: 20 ft./15 ft.
Special Attacks: Paralysis, swallow whole, trample xdx+21
Special Qualities: Darkvision 60 ft., scent
Saves: Fort +16, Ref +10, Will +16
Abilities: Str 38, Dex 15, Con 26, Int 1, Wis 15, Cha 6
Skills: Climb +46, Listen +28, Spot +28
Feats: Alertness (B), Combat Reflexes, Snatch (B), Track, 7 more (2 can be epic)
Environment: Underground
Organization: Solitary, pair, or cluster (3-5)
Challenge Rating: 4+x
Treasure: None
Alignment: Always neutral
Advancement: 25-48 HD (Gargantuan); 49-72 HD (Colossal)
Level Adjustment: —
Paralysis (Ex): Those hit by a carrion crawler's tentacle attack must succeed on a DC 30 Fortitude save or be paralyzed for 2d4 rounds. The save DC is Constitution-based.
Swallow Whole (Ex): A Mystaran gargantua carrion crawler can swallow opponents up to three size smaller than itself by making a successful grapple check. Once inside, an opponent takes 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 19). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A Mystaran gargantua carrion crawler's interior can hold 2 Large opponents, 8 Medium opponents, and 32 Small or smaller opponents.
Trample (Ex): Reflex half DC 46. The save DC is Strength-based.
Skills: Carrion crawlers have a +8 racial bonus on Climb checks and can always choose to take 10 on Climb checks even if rushed or threatened.
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Somewhere along the way we lost the trample damage values in both Cleon's working draft and the main template. Ditto for the original attack that dealt no damage (I added it back, but I may not have done it the way we agreed).