Gamma World-AD&D Thundarrian Cross-over Rules
As it says in the tin (the topic title), Jimm's Gamma World is a document made in the mid-'90s that mixes the rules form 1st ed Gamma World with 1st & 2nd ed AD&D (and a few Star Frontiers items added in), with additional elements to make the game playable to Thundarr the Barbarian. In this game, you can play any of the GW races, plus Cyborgs, and a number of the D&D classes, but altered (e.g. Fighters have been broken down into Barbarian, Savage and Warrior). It could be really useful for making Mutant Future/Mutants & Mazes conversions.
You can snatch it up here.
You can snatch it up here.