Here is a patch that will convert Duck Tales 2's mapper from UNROM to MMC3.
7/25/13
infidelity
Converting Duck Tales 2 from UNROM to MMC3
UNROM bankswap routine is located at $1D3A8 as '999CD3'
MMC3 jsr bankswap routine is located at $1FF10 as '2000FF'
Alter Reset Vector pointer so i can load my MMC3 setup routines
$2000C = 20FF
MMC3 Bankswap Routine
$1FF10 = 0A48A9068D0080688D0180090148A9078D0080688D018060
MMC3 Setup Routine & JMP to Reset Vector
$1FF30 = A9008D00808D01808D00A08D01A08D00C08D01C08D00E08D01E0A2058E0080BD4BFF8D0180CA10F44C88C0000204050607
DONE! Duck Tales 2 is now MMC3! :-D
-infidelity
DuckTales 2 (USA).nes - NOINTRO
CRC32: 40CE2FC0
MD5: EE092394B1E64B8BEE7CA54C3DC7FAAD
SHA-1: 76093EA07A16FDAA8AA58730FD29B4977A264B5E
SHA-256: 6400B8DEDBB6273F5EA01B68C61453F7CF5CAB64EA2A0F57D4D31DD4B983187B