comp 280 magnum or mp 280 cams can't decide!

Engines built like what you want usually run about 350hp. If you port the heads well it will be in the 375 range. I'd run a different intake and carb, something like what rumble mentioned

MM articles are pretty famous for grossly inflated numbers. Like the stock shortblock, stock headed 340 with a xe268H making almost 400hp... LMAO... sure they do. BTW, I can make an engine make ~15more hp on a dyno with nothing more than a few keystroke or a medical device. So yeah, you can fudge numbers pretty badly on a dyno.

Good luck, I'm out.

Pick your parts pay your money.