except for the m codes, they should work for both versions of FRLG, unless it specifies v1 or v2/1.1
Personaly I would use http://www.supercheats.com/gameboyadvance/Pokemon*codes2.htm, just replace the * with the "FireRed" or "LeafGreen"
Don't just click the link, copy and paste it into your url bar and replace the *.