Do you have a world in an older modpack you want to play in a new modpack?
Well I did, so I remapped my world. Specifically, I successfully converted between these major versions:
Modded 1.7.10 from 1.5.2 (i.e., FTB Infinity Evolved era from FTB Unleashed/Unhinged era)
Modded 1.5.2 from...