Using SM64DSe, replace the following .bmds file in your rom with the ones included. Instructions below.

SM64DSe can be safely downloaded here:
https://github.com/StapleButter/SM64DSe
For those not familar with this program, you launch it from SM64DSe/bin/Release/SM64DSe.exe
If you already have this continue on.

>>Backup your rom before proceeding!<<

1)Once SM64DSe is opened, click "Open ROM" on the top left and select your SM64DS rom.
2)Click the "File System" tab and navigate to -
                               data/enemy/bomb_king/ (for Buff)
                               data/enemy/donketu/   (for GMP)
3)Click "bomb_king.bmd" then click "Replace (Raw)" and select "bomb_king.bmd" from the included
Folder. Stop here if this is the only replacement you want.

4)For GMP do the same as above for "donketu.bmd" (data/enemy/donketu/)

Notes about Buff: You cannot fight him on Level 4 - BIG BOMB-OMB'S REVENGE for some reason.
He does work well on his 1st level.


Addition info for SM64DSe here:
http://kuribo64.net/archive/board/thread.php?id=12

The Super Mario 64 DS rom used was (E)(Wet N Wild) which can be safely downloaded here:
https://sm64hacks.com/hack.php?id=439
>>These .bmd files should work properly in any version on the SM64DS rom. However I haven't tried them
on any other version. If results are not as expected please try to import them to this rom.

I did not make these models, I used blender to make it compatible with SM64DS