Honestly... you'll make more power with a cam that doesn't lope on a stock motor.
The E cam and the Crane Powermax 2031 are actually the same cam. They are also intended more for slightly higher revving and better flowing setups than stock. Here's Crane's description of the cam:
"GOOD MID-RANGE AND STRONG TOP-END POWER, REQUIRES MODIFIED MASS AIRFLOW, AFTERMARKET INTAKE, PERF. CYLINDER HEADS AND HEADERS, MUST USE 5-SPD AND 3.55 OR NUMERICALLY HIGHER REAR GEARS."
A lot of people use it in near stock applications because it "sounds good". If you don't mind losing a little bit of power (mostly low-end torque) for the sound then it'll be fine. It will definitely sound good (110* LSA = lope).
If you'd rather have a cam that may make a little more power than the stock cam and work well with the stock parts... check out the smaller cams in Comp Cams Xtreme Energy line, particularly the XE258HR and XE264HR.
In reality though, the stock cam is actually a decent cam for the stock heads and intake. Really, the only reason to swap out a 5.0 HO cam on an otherwise stock motor (meaning stock heads and intake), is to make it sound good. You make pick up a few hp with one of the XE cams or something similar... but it probably isn't worth the work and money. So if you just want the sound, the E303 isn't a bad choice. Just be warned that you may lose a little bit of bottom end in exchange.
