It's very simply:
For convert field model to worldmap model, Just extract both with LGP Tools to Char's folder and World's folder, and for exemple:
-For Cloud: (Char.lgp: aaaa.hrc --> aaga.a) Copy them into the world's folder and rename aaaa.hrc to bbe.hrc and replace
-For Tifa: (Char.lgp: aagb.hrc --> abcf.a) Copy them into the world's folder and rename aagb.hrc to dlb.hrc and replace
-For Cid: (Char.lgp: abda.hrc --> abja.a) Copy them into the world's folder and rename abda.hrc to ata.hrc and replace
finally create a new World_us.lgp
Just it !! I tried and it's work !!
So donwload the release's Cloud AC Custom model of Kula (the GOD ^^) then in the high res folder rename de aaaa.hrc to bbe.hrc and Copy all file in High res folder (include de bbe.hrc that you have created) into the world_us.lgp