too long but my 8 cents worth
Aluminum or steel depends on what you are going to load (weight) and what you are going to haul it with.
If your using a Ford super duty PU or equivelent then steel is all good.
Or some motor homes are built for hauling big trailers (
Diesel is a must)
For Trailex they are great for most car show and go people who want a excellent light trailer with nice features for low cars like the GT.
However most of the Trailex units are 18' or shorter (on the floor) if you plan to haul your toys along with the car and room to move around them then I would recommend a 26' min but I use 28' (anything longer and your out of a good tag trailer size and should use a gooseneck).
Harleys are typ 8' long, drive them both in to the front wall and you will have room for track tires or what ever else you want between the GT or other typical 16' to 18' car with at least enough room at the rear to get behind and check the straps with the rear door closed.
The side doors and placement, winch, over head cabinets, AC, awning & nomal stuff are all options you can pick and choose and everyone offers them.
Suggested Options you might over look (if you haven't towed a bunch b/4):
If using a drop down ramp door have them
add a 3' flap with ground bumpers at the top of the door and you will never need ramps or boards. Trust me I have loaded the GT90 and Indy cars W/o ramps and boards.
Rubber floor is the best "
NO linoleum tile floors" (dew or any rain will make it so slick you will slip and fall on the GT hurting both your head & the aluminum body of the GT and worse yet your pocket book and pride).....:ack
Caulk with clear silicone all around your base floor trim mouldings so you can raise the tongue and wash the floor & rinse with a hose.
Floor or low side lighting helps when strapping and stopping at night to check the straps.
E-track is a system which allows you to locate the d rings anywhere on the floor. I have mine sunk in the floor and this way I can use the trailer to move or haul just about anything and can locate the straps wherever they need to be.
Think Chips gulf sign or the really cool antique the wife just had to have or new garage air compressor and tool box etc.
Another great option is a floor well for the spare tire (hidden with the interior flap door) You will get a flat its just a matter of time (trailers sit in one place for long periods of time)
If your tall say 6' then I recomend a extended hieght trailer. Mine I get all with 12" higher option
Almost all trailer companies including trailex will make taller units, side doors and basically anything you want.
If cost is a factor aluminum frame (featherlight, trailex and so on) are about 50% more $$$ but weigh 25% less.
As soon as you get it home. Take all 4 tires off and get them high speed balanced. Do not listen to anyone who tells you otherwise. Your trailer will stay together longer hinges will last better and your axle/bearing & such will thank you. Plus you will get 2X the life out of your tires. Would you drive a car with unblanced tires???? nuff said.
Photo on Trailex website with a blue GT in it
http://www.trailex.com/viewprod.cfm?id=3&mcat=93&cat_id=93
Pace Shadow GT is a great bang for the buck and everone the others have posted all make good trailers. Pace is the most experienced at car haulers and have lots of standard options.
Here is an excellent site with just about all the trailer manufactures websites.
http://www.roadsters.com/trailers/#race
Now is the best time (winter) and everyone should be offering 10 to 15% discounts (trailex has a inventory 15% off sale now)
Hope this helped