Magnum 300 crate engine - how should it go when tuned up right?

If the carb has vacuum secondaries, make sure they are opening.

Many moons ago, a friend of mine complained about his 66 389 Goat not accelerating hard enough. The choke was designed to not allow the secondaries to open if the choke was not fully opened. (Cold engine.) The adjustment was off. End result: 2 BBL carb.
I had a 72 340 Demon. The Thermoquad had the same fail-safe system: the choke linkage would would prevent the secondaries from opening if not set correctly.
Another friend had a 69 Road Runner with a 440 6 Pack. It ran very poorly at the track. He inadvertently had the end carbs (vacuum operated of course), connected wrong. End result was it was a 2 BBL.

By the way, you can't tell if they are working by winging the throttle while looking at the carb. There's not enough load on the engine.

Edit: Don't know what specs the "stock" cam has, but if similar to a stock 340, it'll stop pulling about 5k or so if the secondaries aren't opening. About 6k if they are.