360 Advice Needed - Autocross / Street Engine Build

Looking back at the starting post here, its still not clear to me how much of the engine has been committed to, but a fair amount has already been purchased.
To make some quick & dirty comparisons on a desktop dyno (Dynomation5), I put the 275 duel energy cam into a 340 (I know its a 360 but this is quicker) with generic 10:1 closed chamber high performance heads. (no experimenting with advancing or retarding the cams.)

FWIW, IF changing cams is on the table:
* The "Magnum Muscle" replacement cam will make more power than the Dual Energy from 1000 to 7000 rpm, except from 5500-6000 where they are the same.
* The XE 268 cam will make more torque and power than either of the other two until 4500 - 5000 rpm. From 5000 rpm up, the 275 Dual Energy cam makes more power than the XE 268.

Take this as trends rather than absolutes. You can always help the upper end in these programs by mild porting of the heads. In real life, that's probably true but you have to know what you're doing not to mess up the lower and mid range. Definately doable - if the heads aren't already on.
My understand of split duration is that it helps keep the power from falling off after peak - that can be useful for both autocross and track when you don't want to, or can't, shift up. The idea it helps when running a cast iron exhaust is one I held but from reading stuff posted by Mike Jones (Jones Cams) and some others, it may not be true.

Running all three cams with the most restrictive exhaust in the software shows pretty much the same pattern as with headers. The XE268's torque advantage becomes minimal compared to the "Magnum Muscle" which still has a noticible top end advantage.

Take this with a grain of salt. I know this program's output is shifted left from where I've seen in real life. In other words it peaks a 340's performance about 500 rpm early.

Finally. In my opinion, if you're running aluminum heads, its going to be hard to make it look like a stock engine. Take advantage of the class rules for the build. Decent headers will make big difference. If you beleive the simulator, you'll have more torque and power the entire rpm range with the Dual Energy 275 and small tube headers, than either of the other two cams using the best cast iron manifolds. Again, take with a grain of salt, but I think its worth consideration - there is more to be gained with headers than swapping cams.

The trick will be to get tuning, especially the timing to work with your combo and available fuel.