I started talking about this in the kaneko label thread here:
Kaneko SuperNova Cart Labels anywhere??
but I figured it'd be better to move the conversation here into the region thread.
... while I had the carts out I tried something I've been meaning to test. the only difference between the different region variants of the games seems to be the socketed roms so I burned some new roms for my Korean Gal's Panic S and converted it to a European region. I might try the same with Saru Kani to convert it to Vs Block Breaker.
So you burned the other regions roms and worked without issues? Cool. Are you using a multi bios on the MB?
yes I'm using the multi bios.
so there are 2 socketed chips on every kaneko cart
on Rom-2-Boards it's u8 and u10 (1MB each)
on Rom-4-Boards it's u4 and u6 (512K each)
so some games came one R4 boards others came on R2 boards, some games could be on either.
my Gal's Panic S was on a R2 board so I used a couple of M27C801 to burn new u10 and u8 chips from MAME. Nothing special about it either, just burned them and threw them in.
So, I went through the mame source and pulled out the different potential CART region conversions:
ROM-2-Board
cyvern <-> cyvernj [M27C801 x2]
galpani4 <-> galpani4k <-> galpanidx (this one is odd as the "dx" version uses 1MB roms and the "4" versions use 512K)
galpanis <-> galpanise <-> galpanisj <-> galpanisk [M27C801 x2]
galpansu (R2) [other regions use R4 board]
galpans3 [no other regions]
panicstr [no other regions]
jjparads [no other regions]
teljan [no other regions]
ryouran <-> ryourano [M27C4001 x2]
vblokbrk <-> vblokbrka <-> sarukani [M27C4001 x2]
ROM-4-Board
galpans2 <-> galpans2j <-> galpans2a <-> galpansu (R4) [M27C801 x2]
gutsn [no other regions]
puzzloop <-> puzzloope <-> puzzloopj <-> puzzloopa <-> puzzloopk <-> puzzloopu [M27C4001 x2]
jjparad2 [no other regions]
sengekis <-> sengekisj [M27C4001 x2]
senknow [no other regions]
The only one I've tried is galpanisk -> galpanise
I plan on trying puzzloopj -> puzzloopu, sarukani->vblokbrk and maybe sengekisj -> sengekis
the only real odd-ball here is Gal's Panic SU, this is Gal's Panic S2 for the korean region but they used an R2 board while the rest used an R4. supposedly all the mask roms are the same so it might be convertible to S2.
If you were going to attempt a cart conversion you'd also want to stick to a donor cart of the same type. So a good donor for Cyvern would be Jan Jan Paridise, and a good donor for Sengeki Striker would be Puzz Loop.
The SU cart might be a key to converting board types though, as they're supposedly running an R4 game on an R2 board. looking at mine there is only 1 jumper wire and I don't see any other modifications (though there are some PALs that might be different)