goose neck towing with K20

[K20chevy]

Does anyone use a goose neck on their 73-87 chevy? I was wondering which one is the best and also what the tow ratings are for a setup like this.

I do have a class 5 hitch below the bumper, which is rated at 12000 lbs (15000 lbs weight distributing), however I know the original tow rating is not as high.

Not sure how much a 78 K20 was rated for towing from the factory. Granted I have a D60 front with 08 F550 brakes and a 14 bolt rear with 08 3500 Dodge brakes, so the brakes and axles can handle way more than what the truck came with stock.

As for the goose neck, were these trucks ever rated for goose necks back then? Or do the hitch manufacturers factor the truck capability in, when they release a hitch for a specific truck? Or is the rating just for the hitch itself?

Just trying to figure out if a goose neck is worth the extra work on these old trucks or not...