im a big fan of not going to the hardware store. ill tear something apart and keep the good bolts. the only thing i bought for this project was the cold rolled steel for the rear axle. all tubing is 4 side welded. i think it should do 400 pounds with little issue. it is now rhino lined inside the tub, and has a nice hand built pillow inside, ill update pictures when i can. hard to do while hiding it from the kids for my oldest s birthday. im going to add a faux shifter knob off the right side and some custom side rails.Nice job, but I think it could do with more bolts - you have enough in those cans in the background
cute kid! i over engineered everything, it can be made MUCH simpler. google is a good starting point!