318 Stroker

I don't think your going to find a 318 to be bored out to a 4.04 LOL!

3.31 X 3.91 = 318
Stock
3.31 X 3.94 = 322.85 (.030)
Easy overbore
3.31 X 3.97 = 327.79 (.060)
Possible overbore, probably not advisable.
3.31 X 4.00 = 332.76 (.090)
Extremely doubtful overbore
Sonic check before any work is done.