The 300hp Magnum crate has the factory 5.9L production camshaft in it. So there's just not much power on the table. But - it should be a lot peppier than what you're saying. At least spin the tires hard in first. IMO the 5900rpm shift is way too high for it. It would be quicker shifting at 4500. The engine's out of air by then with that cam. In terms of tuning - the Demon carbs are not my favorite. They are very finicky when set up properly. Especially in a state like ours with nights where its 75 with 90% humidity and then mid 50s with no humidity the next... Plus the 650 wet flowed Demon is probably too much for that package. That's close to a 750cfm dry flowed carb, and again, that's too much for a mild 360 with no cam.
Magnums don't like timing. So you need to set the timing curve, then set the carb. If it was me I'd look at initial around 15*, with the centrifugal of 17*, all in by 2500. I'd run a vacuum advance too, off ported vacuum. Rebuild the carb and pay attention to the power valve ratings and cleaning the parts. Demons are famous for having poor cleaning and I've found "hanging chads" of aluminum left in the metering blocks in different sized carbs years apart.
If you are used to an 02 then either install one or find someone that doesn't need it.
