The only downside of swapping the back is that Nintendo uses their own type of screws. I don't have a gamebit screwdriver right now, but when I do... Sin and Punishment, here I go! 
Well, you'd need gamebit drivers no matter what route you went, whether opening the console or the carts.
Actually N64 is super simple anf safe to open.
Just unscrew 6 screws, and lift the top of.
Thct slot is attached to the top..
It's actually the exact same as the SNS-001, and the SNS-101 has even fewer screws.
Still, need that gamebit no matter what.
But hasn't the back of an US cart english text on it and JP backs have jp text?
Would ruin the whole cart in my book if it has mixed regions then....
I'm working on repro cart back labels for the SNES and N64 right now to go along with the case shells. Doesn't hurt to have a variety of smaller products to go along with the cases
