Here is a full level hack for Mega Man 3 which changes all the level layouts in the game.
Mega Man 3 (USA).nes - NOINTRO
CRC32: 452D8089
MD5: 75B924155CAFEE335C9EA7A01BFC8EFB
SHA-1: 53197445E137E47A73FD4876B87E288ED0FED5C6
SHA-256: EDDBE571CF0A201BA9D090FBACE9843C9C9DD4053051649F2575B088752F4675