5th Wheel Rails with 4 bolts

I am looking to purchase a 5th wheel; I bought a Chevy 2500 with an unknown brand of "Bracket Kit" that attached to the frame. This bracket kit has 4 5/8"slider nuts with corresponding holes in the bed. The truck did not come with the rails. Most of the old-style rails I have seen (and I am no expert) have 4 bolts on each rail for a total of 8 bolts that secure the rail to the truck. I bought a couple rails, drilled 4 5/8" holes and secured the rails with 4 5/8" grade 8 bolts. Is this secure? Is there a equation that I can apply to determine if the 4 5/8" bolts are as secure as the 8 smaller bolts on "Normal Rails" Does anyone know what brand of "Bracket Kit" has 4 nuts? I don't what this rig coming disconnected from the truck. Thanks