Yepp,... You need:
-A MC, which is recognized by the PS2 without a Boot-Disc
-Some knowledge on how to create the PS1-Exploit.
1. Create the PS1-Exploit for your JAP-PS2 (at best with "ule" as BOOT.ELF).
2. Copy the necessary files to your Target-MC (where FMCB should go on...) with your PAL-PS2.
3. Insert the MC to your JAP-PS2.
4. Start the PS1-Exploit (normally "unofficial LaunchELF" should start up).
5. Go to your USB-Device, where the Nooby-Package should be and start the FREE_MCBOOT.ELF (remember, not to miss the X-Modules in "MODULES"-Folder).
6. Install FMCB and you´re ready.
Btw.: You´ve luck. You can install FMCB for both of your PS2s on one MC.
The NTSC/JAP PS2 searches its OSD-Update in another folder, than the PAL/EU PS2, so you can have both on one.
Both still share the same "BOOT"-Folder and the "SYS-CONF"-Folder.
Edit: @Bootleg&dj: His modded PS2 is a SCPH-39004-EU PAL and his Target-PS2 is a SCPH-10000-JAP NTSC.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux