Well, I'll see if I can clear something up first. Hooker Super Comps don't come in 1 5/8", only the Hooker Comps do, part #5901. Those also go below the steering linkage, so the ground clearance is pretty horrible.
Hooker Super Comps, #5115, are 1 3/4" and stay above the steering link, so they have pretty decent ground clearance, much better than the 5901's. I have 5115's on my Challenger. They should also be an increase in power over a set of 1 5/8" headers on a 408. Maybe not a big increase, but they'd help a little especially if your heads are flowing good numbers. That power would be mostly on the top end though, so you probably wouldn't notice it much on the street, but your dyno numbers would see it and probably your ET's at the track.
As far as TTI's or Doug's, the TTI's also come in the 1 3/4" tube size, so that should be a similar improvement in power vs. a 1 5/8" header , and an improvement in ground clearance if you have the 5901's.
The Doug's header should provide the best ground clearance. I have a set on my Duster, and bought them because they sit about 3/8" higher than the TTI's. You can't get any tighter to the frame than a set of Doug's 453's. But, they're also a 1 5/8" header, so they probably wouldn't provide much of a horsepower change.
For an E body the TTI's are probably the best option. The Hooker 5115's are pretty respectable though. The Doug's are great headers, but unless you're super concerned with ground clearance you give up a little of that tube diameter. I like the Doug's for A-bodies, just because they fit so well and because TTI's are the only other option. For an E body you have more space for the bigger tubes, and more options with the 5115's.
