In general, a class 3 hitch has a #500 tongue and #5000 GTW (Gross Trailer Weight) rating.. I've seem some aftermarket class 3 hitches that have 750/7500 respectively..
My factory tow package hitch is the 500/5000 variety, but it also has a 1000/10,000 rating when it's used with a WD (Weight Distribution) setup (class 4).. I think even that aftermarket hitch was the same rating when using WD.. (in other words, it just gives you a bit more capacity on the class 3 side).
Now, all that being said, you should still be mindful of what your trucks GVWR (Gross Vehicle Weight Rating) is and also your trucks rear GAWR (Gross Axle Weight Rating).. You could bolt on a class 5 hitch (1200/12,000 all by itself), but if that amount of tongue weight exceeds either of the above trucks GWR, then you are overloading your other ratings, so it does not matter what the hitch rating is...
For example, if you tossed in a yard of sand in the back of your truck and also wanted to tow a trailer, you would be SOL... Because the load in the bed all by itself is going to exceed your trucks GWR's before you even hitch up!
What APT is saying is that you also have to be mindful of the weights that are already on your truck, then figure if you still have enough capacity for the tongue weight of a trailer..
What kind of 24' trailer is going to have a #370 tongue weight?? Must be a car hauler, or a boat trailer?? My 22' Travel Trailer has a #600 tongue weight! I'm a "tad" over my trucks GVWR when I'm all loaded up for a long weekend camping trip, but it's not 'that' much over, and the truck does not 'look' overloaded, so I don't get bothered with it! Yeah, yeah, I know the Weight Police would be all over me, but I know my truck and you don't, so blah, blah, blah!
We need a bit more info to tell you what you should do, so give us your truck specs, the trailer you are hauling and if it's just a trip around the block or a 1000 mile adventure!
Mitch