What do you guys think?

I'd also guess 375-385 hp and BTW don't expect that cam to pull 13 inches of vacuum. I ran one in my 360 with 9.95:1 compression (actually calculated, not guessed) and it only pulled 7.5~8 inches of vacuum. Other than that it's a pretty good cam. I agree with Moper about dropping the spacer. A bud of mine that has a hot 340 in a 67 Cuda has that intake tried a spacer and it made it run worse and hard to tune.

Your bud's setup is similar to mine except I have 3:73 gears and ported X heads. With street radials it don't' hook good at all. Once it hooked good enough to run 12.80 My car might be heavier than yours as it seems to be a pig weighing in at 3440 with a half tank of gas. Add my lard butt and it's 3625 lbs. From what I've seen most Dusters run about 200 lbs. lighter so that's an approx. 2 tenths advantage for your bud. If yours hooks good it should run high 12's no problem.