I don't know of any published rules.
Armor Types are easy to convert. You can also use the template rules in Creature Law (beta) to get level-appropriate OBs and skill bonuses.
Spells can be hit or miss, but I haven't found it too hard to convert even unique D&D spells into a RM equivalent. (I've done a couple of 5e module conversions to RMU and just did it all on the fly).