You didn't say what year the engine is, and as far as I know (old and forgetful, and some thirty years ago) there isnt too much diff. in 396/402s. My experience is from the early seventies: I had a '68 SS396 Chevelle that I put an Isky cam(s), Weiand intake, and Holley double ender, and headers on, and ran in the low 12s and high 11s, on street tires and premium gas. They can be built quite well, in my estimation, and I wouldn't pass one up, if it is rebuildable. One of the rod mags (Street Rodder?) did a build on one recently, and got pretty decent numbers out of it, for a mild build.