Chassis dynos, like engine dynos, can be all over the map.
I think that cam is Magnum 280H, 280* at .006 lift and about 230* at .050 480 lift.
What heads are on the engine. Basic stock rebuild with a valve job or cleaned up?
Two things that are hurting IMHO, carb and intake. Rich lean conditions can make a huge difference in power/torque. Did you get a readout showing the A/F's throughout the pulls?
The performer is not the best for getting power. It's basically a stock style 318 manifold in aluminum. The engine would make more power with a holley on it. Seen 20+ hp gains swapping out a correctly tuned ede to a holley.
Like Demonseed mentioned, check the initial timing, get it right, and your all in point. Try to get the all in point in the 2500 area.
A disaster would have been losing the engine during the test, what you have, is the opportunity to get the engine running better. Don't sweat it.:thumblef: