69/70 are the best 351w heads hands down, problem is they dont have hardened seats, so you'd be spending money on seats which isn't cheap(labor wise) the next best set of heads is the 88+ 351 heads only because they have hardened seats, i dont know what kind of setup you're building exactly or what your smog laws are, but you can do a little bit of smog equipment removal on the heads for a little more power