The 5th Wheel type and the regular gooseneck hitch are two different type of hitches, altho they both are hooked to the center of the truck bed.
I agree, I wouldn't pull it with a bumper hitch.
If the trailer max weight (trailer with truck on it) will be 14,600 and your firetruck weighs 9640, it looks like the trailer itself can weigh up to 4960, if my math is correct, but allowing for various extra gross combined weight (extra passengers, tools, equip, etc) you will want to keep the trailer weight somewhat lower than that.
When it comes to weight, it's nice to be a decent amount under the max, both for legal and safety reasons.
Bill
