Trailer weight is the first, and most important factor in determining whether or not your truck is suitable for towing the trailer you have in mind. To determine if your truck is capable of towing a given trailer, calculate the horsepower-to-weight ratio. The basic standard is a ratio of 35:1. That is, 35 lbs. of GVW for every horsepower.
To calculate this ratio, multiply you engine's rated horsepower by 35, then subtract the weight of the truck, including passengers and luggage. The resulting figure is the ideal maximum trailer weight that you can tow. One point to consider: a numerically higher axle ratio can offset what appears to be a low trailer weight capacity. If the weight of the trailer that you have in mind is somewhat higher than the weight you just calculated, you might consider changing your rear axle ratio to compensate.
There are three kinds of hitches: bumper mounted, frame mounted and load equalizing.
Bumper mounted hitches are those which attach solely to the truck's bumper. Many states prohibit towing with this type of hitch, when it attaches certain truck's stock bumper, since it sometimes subjects the bumper to stresses for which it was not designed. Aftermarket rear step bumpers, designed for trailer towing, are acceptable for use with bumper mounted hitches.
Frame mounted hitches can be of the type which bolts to two or more points on the frame, plus the bumper, or just to several points on the frame. Frame mounted hitches can also be of the tongue type, for Class I towing, or, of the receiver type, for classes II and III.
Load equalizing hitches are usually used for large trailers. Most equalizing hitches are welded in place, they use equalizing bars and chains to level the truck after the trailer is connected.
Check the gross weight rating of your trailer. Tongue weight is usually figured as 10% of gross trailer weight. Therefore, a trailer with a maximum gross weight of 2,000 lbs. will have a maximum tongue weight of 200 lbs. Class I trailers fall into this category. Class II trailers are those with a gross weight rating of 2,000-3,500 lbs., while Class III trailers fall into the 3,500-6,000 lbs. category. Class IV trailers are those over 6,000 lbs. and are for use with fifth wheel trucks, only.
When you've determined the hitch that you'll need, follow the manufacturer's installation instructions exactly, especially when it comes to fastener torques. The hitch will subjected to a lot of stress and good hitches come with hardened bolts. Never substitute an inferior bolt for a hardened bolt.