Paul, the first thing you must consider is how much weight can your tow vehicle pull per the manufacturers GVWR located on the sticker in the drivers door jamb. The GVWR of the trailer cannot be more than the GVWR of the tow truck or you are considered overloaded per DOT regulations, even if the trailer is empty. Most trailers with 5-lug 3500# axles can be safely towed with a 1/2 4wd extended cab truck or larger SUV (Suburban, Tahoe, etc.) without any problems. Just make sure you have the largest engine available for your vehicle, and the lowest gear ratio possible. (Torque is what you need, not horsepower). Any trailer with the 6-lug 5000# axles will need either a 1500HD truck that has the 3/4 ton truck axles, or you will need a 3/4 ton or larger truck.
Now without knowing what your vehicle is, a 20' enclosed trailer is more than enough to haul your Camaro. I have a 20' Haulmark and when my 68 is in the trailer there is another 4' of room at the front center (the front wall is not flat) with a foot or so at the rear. Let me know and I can post some pictures of the trailer with the car loaded in it. You can go to a 24' trailer but you will need the larger 3/4 ton truck for towing as most, if not all of those trailers have the 5000# axles. Two mandatory items are a weight distributing hitch and a sway bar, or you will not enjoy towing on the interstate when a truck passes you from behind. I have hauled cars as large as Chevelles, and mid 80's SS Monte Carlos with room left to spare, not much, but enough to keep tools and equipment up front.................RatPack...................