400rwhp for a 347 N/A is at the upper range of the spectrum, but certainly possible. A 347 has 45 more cubic inches working for it than the 302 or an increase in displacement of roughly 15%. In terms of horsepower, the same hp to displacement efficiency would grant a 302 about 340rwhp. Having a N/A 302 making 400rwhp would be like a N/A 347 making 460rwhp. Not impossible, but very unlikely for a streetable car, unless you think there is an easy 75hp more in your friends 347
