My Dart Swinger Project!

So is there someone out there beating a 6 month warranty for $400? Of course an extra 200 for the manifold. I really don't understand why you need a new cam for it right away? I mean a nice smooth running engine to begin with wouldn't be a bad idea. You can get stupid later.
I have a few concerns with the magnum. One is cracked heads everything iv read says the heads will be cracked and may need replaced. That's a huge concern. The intake is another factor more money.
I found a 360 out of a 92 truck 250 bucks that may be a better deal than the 75 318.