I am at Dans house right now and have just confirmed that my N64 mod to play Jap games works.
It was very easy to do but  was afraid i would hit something vital inside of the system and keep it from ever working.
Basically all i had to do was chisle away the plastic pieces inside the cart slot.
I have ALOT of SSB, F-Zero X and Mario Kart 64 to play tonight.
So FYI to anyone who has Jap games and wants to play them.
The caveman method i used is flathead screwdriver and hammer.
A more civilized way to do it would be using a dremel or similair tool to acieve the same thing but with cleaner results and much smaller chance of destroying something inside.
And of course the professional way would be to pick up one of these bad boys.
http://www.electricquarter.com/sbit.htm