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I ran a quick search for you and came up with this... Hope it helps .
Fulton bolt on pivot coupler kit : Fold away coupler shortens trailer by 2" for storage fits 3"x4" trailer tongue class III handles 5000 lbs models 22200 1281 128120 available at www.buildersfavorites.com
I installed a roll bar in my Mustang (yes It's worked 850 HP and scarey fast) and to my surprise, the manufacturer also recommended high strength bolts for installation instead of welding, I used the high strength bolts (3 marks on bolt head).
Matt Whalen (mw)