Like John said stay off the bottom of the page.
If you want to feel the power of your engine then build for torque, not peak power (at the highest RPM obtainable for your engine; that is strictly for racing, not the street). Look at RV cams or even marine cams that build torque by offering higher lift to duration numbers. As to lifters flat tappets are dead. Do not even consider a flat tappet cam. You obtain better cam profiles with a roller cam, and a roller won't destroy your engine the way a flat tappet cam does when you wipe a cam lobe do to the lack of ZDDP in modern motor oils.
That said all the cam information you see on the page is for a 350. If you had a shorter stroke 307 you would subtract duration, with a longer stroke 383 you have to add duration because the air needs more time to flow into the cylinder with a larger displacement engine. You are still looking for a cam with highest lift offered with the least duration.
Duration is a measure of how soon, and how late, the valve closes. You can not build compression or make any power with the valve hanging open. Longer duration cams are used in race cars because they rarely fall below 5,600 RPM: which is near the upper limit of a lot of hydraulic cams. LSA is also important. The larger the cam's LSA the smoother your idle will be. Additionally the longer the LSA the more the cam will be building up your torque curve flattening it out. The shorter the LSA the peakier your torque curve will be and the motor will only make power at the top of the RPM band.
You are striving to increase the area under the torque curve on a killer street engine. To accomplish this you want a longer stroke, higher compression and increased Volumetric Efficiency (VE) also know as cylinder filling (that is the job of the heads thought not the cam). So consider increasing you rocker arm's ratio to increase the lift at the valve without adding a lot of duration.
Big Dave
