First, let's get the numbers straight.

The two games that were originally given the wrong numbers in the U.S. are Final Fantasy IV (Cecil, Rosa, Golbez), which originally came to the U.S. as Final Fantasy 2, and Final Fantasy VI (Locke, Terra, Kefka), which originally came to the U.S. as Final Fantasy 3.

Both of these mistakes have been fixed, and all U.S. releases since the original SNES versions (3 for Final Fantasy IV, 2 for Final Fantasy VI) have used their proper numbers. Pretty much everybody you'd ever need to talk to on the subject knows them by their correct numbers, so don't confuse things by saying "Final Fantasy Right-Number, which is Final Fantasy Wrong-Number in the U.S.". (Especially considering you got the numbers wrong.)

Second, there are already editors available for Final Fantasy VI; we got a bunch of 'em here at RHDN. Just search the Utilities for "Final Fantasy" (yes, some of them are listed as being for "Final Fantasy 3"""; can't change what the U.S. ROM is called). The ASM-free but by far more tedious way to go is by manually editing each and every monster in the game to dump EXP and Gil on the player. For each individual monster, this is probably as easy as changing a number in a text box. But again, you'll have to do it for every monster in the game.