Cam Duration Vs Lift

This is a small block 400?

Neither of these cams are going to work very well.
As was pointed out, your flow falls off after .500" lift so opening the valves much further does nothing but slow down the cylinder fill and add stress to the valvetrain. With that said, .525" is not really a problem with your heads because it is only open that far for a very small part of the duration.
The 290 duration cam will make more power on top while the 270 cam will have more bottom. I would rather see the 290/240 @.050" duration with the .525" lift.
I don't have all that much experience with these "new" cam grinders but I do know that Clay Smith will give you what you need at a fair price. These guys have been in business for about 80 years and they virtually invented the custom hand ground cam. If you tell George your vehicle info and your wants/expectations, they will grind you a cam that will give you what you want. The C-304-6-B (solid cam for SBM) is 308 adv./258 @.050" lift, .525" and makes big power on a 340 from 2800 on up to around 7000 rpm. In a 400CI engine that same cam will make power at a little bit lower rpm. Obviously, you would need at least 3.91/1 gears to use this cam, but it's just an example.
The cheater cam you listed would start pulling at about 3000RPM and keep pulling to around 6800RPM. It would work great with your setup, but you may benefit from 1.6 ratio rockers...since the lift is a bit short of your peak flow numbers.
You are kicking around lift numbers that would make your engine run like crap. If you try to run lift numbers above around .525", it will not run good at all.
T67 nailed it! Those numbers that he suggested are very similar to the Clay Smith cam that I have.

I still don't know what you mean by "usable power". To me, usable power on the street is power under the curve...a wide power band that starts fairly low in the RPM range. Usable power on the dragstrip is a little different, since you are going to be at wide open throttle for pretty much the whole time.

e-mail: [email protected]
or phone (714) 523-0530
Monday - Thursday: 9am to 6:30pm

P.S. IMHO, running a hydraulic roller in a motor with heads that do not flow above .500" is just a waste of money and a step backwards. The solid flat tappet cam will outperform the hyd and the hyd roller cam at this level.