I don't think it's mapper was ever used on any games in the US, so no, not very easily.

I just bought a splatterhouse which I should have from Japan in a couple of weeks. 

I plan on putting the english translation in the famicom cart for myself.  The splatterhouse cartridge is larger than a normal famicom cartridge, so I don't know if the splatterhouse circuit board will fit in a nes cartridge shell with a famicom adaptor.

Ask me about this in a month if I don't post. 

If it all works out, I'll gladly make a reproduction.  Unfortunately, since it would require an original famicom splatterhouse and possibly a famicom adaptor, it would be more expensive than a regular repro.

the rom i have uses mapper 3 - CNROM.  This is a very common mapper used on american nes games.  heres a list of the mappers for us games:

http://www.parodius.com/~veilleux/boardtable.txt

I had thought you had some kind of hacked rom, but I think you're missreading the header.  This is an extended ines header and therefore mapper 19.  You know that it's an extended ines header because of byte 7.  This means strange board that isn't reproducable without the orignal famicom game.

I believe that cajones was last updated in the early 90's and then that the extended nes format came out after 2000.  Therefore, that program will not give an accurate reading of most odd carts.  There were a ton more odd circuit boards and chips for the famicom than for the NES.  Therefore, cajones will be much less accurate for famicom roms than NES ones.

I would suggest a good hex editor like transhexlation:

http://www.romhacking.net/?Category=13&Console=0&Game=0&Author=0&Recm=&Level=&ut...

Then check this out for how to read the ines header:

http://nesdev.parodius.com/neshdr20.txt

If anything confuses you, just email or pm me.

Well, there's good news and bad news.

The good news is that the circuit board is nice and small and will easily fit in a nes cartridge (with a fc to nes converter).

The bad news is that it doesn't matter.  Here is a picture:




Those blobs are glop tops.  They're the inside of a rom chip that's directly attached to the circuit board and then covered with a epoxy that seals right to the circuit board.  Unless a comparable board with the namcot mapper and regular chips can be found, a reproduction's not going to happen.   It would be simple to put the japanese game in a nes cart, but I believe the plot has a decent amount of words to it...

Perhaps namcot used roms in another compatable game (maybe even some copies of splatterhouse used roms, but glop tops are more common in famicom games).  It's hard to find information on famicom game internals and I'm not going to try buying random namcot games to try... 

Basically there's a little hope for someday, but not for now...

Yeah, it's namco 106.  Maybe I'll try a copy of that game next time I order stuff from japan.  Since this cart was in a big order I just got, it will be a little while! 

So many of the famicom games are hit and miss for glop tops.  I've opened up a few goonies 1's and found both chips and glop tops (neither was a pirate).