318, to stroke or not?

Based on what you want, and the three items you listed, stroking is the answer.

The beauty is the streetable horsepower you can get from stroking; a super mild 224/230@50 and .500/520 lift cam would get you somewhat close to 400 if those heads have good flow numbers and some long tube headers were attached.

I got my eagle SIR I Beam rods for $100 at mancini in January and my 4" eagle crank through campbell enterprises for $335 (+$75 shipping) last month for my 318. It's not that expensive if you shop smart.