Just bought a new 05 f550 cab and chassis and had a flatbed installed at a local trailer shop .Well its a 8'by8.5' with headache rack and a goose neck .Got truck back the bed has 3" channel stringer parrallel with frame of truck and then a 4x4 peice of pressure treated wood .Here is where I got a question :confused: they mounted 4"channel from the bed stringer to the frame of truck with 2 grade 5 bolts total of 6 of these mounts .There is no ubolts around the frame of truck to the stringer like I've seen before . So should get ubolts made and install and then remove the grade 5 with grade 8 bolts?? Was also thinking about a plate from stringer to frame right at the gooseneck mount where there is none now. Any help thxx

It should have like 3 pieces of plate,channel,ect from the mainframe of the flatbed{in your case the 3" channel down next the frame and they should have like a 5/8" or bigger bolt in each one through the frame.Grade 8 bolts couldn't hurt.I wouldn't use u-bolts.We have never had any problem with our flatbeds coming loose.Ours ore mounted with 7/8" bolts,a total of six,3 on each side.I have one on my D-Max that goes through the top of the frame and through the flatbed frame that way:confused: not sure why they installed it that way but it seems to work good.

will check bolts if there is one mounted like you said thru bed and frame .All the flatbed on the the trucks I have at my work all have u-bolts and weld on the rear of frame by 2" reciever

btt