Auto Krafters has them, they're 1 1/2" diameter primary tube and cost around $350 US. Tubular automotive has them, but from what I hear they dont fit real well. Or, if you know a little about welding, and have about 2 weeks spare time, you could build your own like we did. Still had to smash them quite a bit, even with "notched" shock towers. Point is, there's no real easy way to get a 351w to fit and still be able to use headers, at least not that I know of. Mustang II front end sure looks like the way to go, loads of room for most any header you would want.