I have the ARH headers, but have not installed them yet. I can't comment on how they perform, but wanted to share my observations. The quality is top notch. The welds and tubes are excellent quality and they make a smooth transition from the round tube to the "D" shaped port at the head. Excellent engineering on their part. They are ported a bit to closely match the gaskets they supply, which are a bit bigger than the stock gaskets or stock head ports. This creates a nice anti reversion step where the head and headers meet. I ported my heads and was able to raise the exhaust port roof a decent amount due to the excellent design of the headers port, so much that I will not be able to use the stock metal gasket. I was very happy the way this turned out. I come from motorcycles where the good head designs all have high, relatively straight ports in the exhaust, some amazingly so.
I chose ARH as they appear to be the most equal length of all the headers out there. The MOPARS also look great in this regard, but are relatively harder to come by and are made to go with a 2.5" exhaust. ARH also has a very good collector design, right up there with Burns Stainless, who's exhaust parts are all top quality. I like the slip/clamp on 3" mid pipes that come with the ARH headers. They also put in extra O2 sensor bungs on individual tubes where I asked them to, no charge. Delivery was fast, though they had to make them to order, but the wait was short. I got the best price ordering direct from ARH.
One mod I had to do to fit on the heads (heads on bench), was to grind some of the aluminum on the underside of the top lip so they would bolt on smoothly. This would be hard to do with heads on the truck, so alternatively could grind the top of the header flange to make fit. Without grinding, they could probably still fit, but there would be some interference fit. I plan to give feedback to ARH on this.
