You can run any scenario from any RQ-like game with any other RQ-like game with varying levels of difficulty.
Mythras/Legend/RQ6 - Very Similar/Easy to use
RQ2/RQ3 - Very Similar/Easy to use
RQ2/3 with BRP or OpenQuest - Similar/Fairly easy to use
Revolution is similar to Mythras/Legend/RQ6, but treats skills quite differently, so is a bit harder to fit into Mythras/Legend/RQ6, but should be easy enough to use Mythras/Legend/RQ6 for Revolution.
After all, does it matter that a troll NPC in RQ3 has Sneak rather than Move Quietly, or a troll in Legend has Stealth, or a troll in Revolution has Stealth [Move Quietly]? As a GM, not at all.
What I do when using supplements written for one system in another is:
Use Characteristics/Skills/Hit Points/Armour/Hit Locations as they are in the supplement, no need to convert, no need to recaulculate
Use spells as they are in the rules you are using, if the spell isn't there then use the original spell description
Recalculate Strike Ranks, if your systems use different types of Strike ranks, so for RQ2/3 keep them the same, Mythras/Legend/RQ6 keep them the same, but using an RQ2/3 scenario with Mythras/Legend/RQ6, recalculate them.
Do all recalculations on the fly, rough and ready, they don't need to be exactly right