Headers - Shorties or Long Tube?

[SleeperGT]

Now that my car has been stabalized from the last round of upgrades, car is actually running GREAT, I'm ready to cause trouble again and I think I want the next upgrade to be headers, provided everyone agrees. I currently have 2 1/2 "exhaust (x-pipes) from manifold back with Magna Flow mufflers and dual high flow cats.

With my current setup I'm thinking I should go with Long Tube headers which should give me the most hp gain. If you have had direct experience with this upgrade on a 4.6 GT with a S/C please comment, the good, the bad and the ugly are apreiciated. Also, what have peoples experiences with Shorties been? My other questions are as follows;

1. I've heard long tubes can cause a clearance issue, how far do these things hang down, can you actually see them in the profile of the car hanging beneath the front of the car?

2. What kind of HP gaines can I expect? I'm guessing I'm running about 370 hp at the rear wheels right now. What should I expect to gain?

3. Who makes the "best" set of long tubes, by this I mean quality and performance. I was thinking of going with a set from Ford Racing.

4. Will adding them cause any issue with my current tune, and will I have to get the computer reprogrammed? My biggest concern is causing detonation. Extra hp is great, but if I get detonation or other issues than it's not.

5. What should I expect to pay for a good set?

6. How difficult is the installation?

All input is greatly appreciated!!