6.5 Jap from .35 Rem brass
The .010 difference in the head diameter does not make a concernable difference except when forming and reloading the brass. Make sure you use a .35 Rem shell holder. I have shot my Type 38 hundreds of times with this brass and it works just fine. I also keep it separate from the "real" 6.6 Jap brass.
If you have any concerns don't do it.