I went with Dougs on a 383 in a Challenger, and have found them to be very good. I used copper gaskets, and tightened them again after the first run and about 30 minutes of cool-down, as instructed. I don't drive the car a lot, but I've checked the bolts occasionally and they have never needed anything else once hooked up properly. No leaks, no cracks, no pinging noises. Coating is holding up very well after 6 years and about 8k miles.
Several good products out there. The makers vary the tube routing so look carefully, see if you like the routing, and check into clearances for things like mini-starter, tight-ratio arms and boxes, etc.