Rules for Converting Encounter Critical PCs to Tunnels & Trolls

Key Attributes

Strength, Dexterity, and Luck remain the same.
Intellect becomes your Intelligence score.
Leadership becomes your Charisma
You get the choice of either using your Dex score or rolling 3d6 for your Speed, but you must pick before you roll the dice.
Either your Adaptation or your Robot Nature score become your Constitution, whichever is higher.
Either your ESP or Magic Power score become your Wizardry, whichever is higher.

Professions

Psi Witches become Rogues, unless they qualify to be a Paragon (f.k.a. Warrior-Wizard), in which case they can be one of those.
Doxies, Criminals, Pioneers, and Encountresses can become their choice of either a Rogue or a Specialist.
Warlocks become Wizards.
Warriors remain Warriors (duh).

Levels Past One

For each level past one, the character gets a bonus number equal to their level which can be spent on any one of the following:

Add the bonus number to Strength.
Add the bonus number to Constitution.
Add half the bonus number to Strength and half to Constitution.
Add half the bonus number to any other stat.

When halving for purposes above, any fractional points are lost. Additionally, each level up must be spent individually, e.g. a third level PC must first spend 2 points and then 3 points.

Spells

Newly converted Wizards get access to all the spells available up to their level, even if they cannot qualify due to low Int or Dex. Exception: If the referee is allowing the Wizard to keep their old Warlock spells, they only get access to the first level list.
Newly converted Rogues get one first level spell per every character level they possess.

Equipment

Any item on both the EC and T&T lists may be retained.
If the item in question is a weapon or armor that the PC can no longer use due to new Str or Dex minima, they may take a free downgrade to a lesser but equivalent item.
Any items not in both the EC and T&T rules are subject to the Dave Arneson City of the Gods spot rule*: each PC may pick three items to retain. The nature and extent to which they continue to function in the new setting are the sole discretion of the referee.

*Gary Gygax once brought his PC Mordenkainen to visit Arneson's game for an expedition to the legendary City of the Gods. Dave saw the vast number of magic items on Gary's charsheet and was underwhelmed. He immediately ruled that Gary could bring any three of them and a potion of extra healing. A recounting of these events used to be on the intarwebs somewhere but at the moment I can't find the dang thing.