71 K10 Towing capacity help

[Chris 71 K10]

I have looked thru a bunch of threads and found a few varying things. I know different specs and ordered options can come into play as well. I am sorry if everything here has been covered but I am dense so here goes.

I have a 71 K10 longbed and need to pull a horse trailer. 2 horse trailer, it has trailer brakes, 2 axles. Weighs about 2400 pounds empty and each horse about 1400 so close to 5500 pounds with 2 horses in it. I will be pulling just the trailer sometimes, with 1 horse sometimes and sometimes with 2 horses.

The attached pics show my truck spec of heavy rear springs, posi traction RR axle, front stabilizer etc. . .
It has a 350 motor, NP204 and 3.07 gears (not 3.73)

In the charts I have seen the 3.73 gearing usually shows a heavier tow capacity. Does this mean it that mine would pull it safely just not as fast especially up grades. Speed is not that important but I do want to be safe.

Not sure what much of the difference really is besides gearing on my K10 compared to the K20's either?

Again I am pretty green and just regurgitating things I have heard so it may be off or plain wrong so any real help/input would be great!

Thanks ahead of time, great board as always!

The Green truck in the pic is mine for fun reference last week at The Desert Race in Johnson Valley CA. Not a lot of shade so we made our own.