This isn't a big rig chassis. The suspension will out move the frame, by design and never see the weight or box/bed size the big trucks do. I am building it to be rigid, like a coil sprung frame should. Due to the Duramax in front, I am thinking about full frame 3/16" box plates. The engine crossmember is round 1.5" OD, .25" wall tube. The trans and transfer case cross members will be too.
The internal 1.5" OD, .25" wall cage will also tie into the frame, with bushings and we have plans to redo all the sketchy body mounts. When I say body mounts, I mean the 4 C30 based that are barely scabbed on. This will get 6 new ones, plus the cage mounts and a 2"x4" rocker guards with drop down steps.
My rear side plates are flanged and they're also 2 pieces of 3/16" thick laminate. The hitch plates also work as my outside, frame extension fish plates. So my frame extension is triple 3/16" laminated... The box tube is fully welded and covered the 4 .5" bolts used to originally put it together. Still doing final weld out, but I have to fit a Chi-com 17,500 lb. winch back there, along with a 52g stainless tank in a 3/16" thick skid plate.
The rear winch gets a custom winch plate, that mounts the winch upside down and ties into the frame's top and bottom flanges. I'll admit, I am cheating as I have the old transmission cross member that will give up it's upper flange tie ins.
The truck will be around 9,500 lbs. when done. It's titled at 25,999 lbs. It's one of the reasons I went with 15.5" brakes with 6 pistons. if the Sterling 10.5" isn't up to it, I have a D110 that I have to re-gear to match to 4.30 the front. I'd also stick an e-locker in it.
So 15K lbs. on a trailer is reasonable. The rear hitch won't see more than 14K, but it's all Class 5 rated (15.5K lbs.).
So, now that the suspension is mostly done, I am doing the frame, front, back to front. Hitch, winch, 52g fuel cell, modular fifth wheel and goose neck hitch, divorced Ford NP205, Allison, Duramax and then all the radiator support mods then another 17,500 lb. winch in a front bumper. These winches are cheap, work well but are getting more expensive... bought 4 for 270 (each) shipped and they're now 100 more.
The fuel tank will have a bed side fill bolted to the old sending unit location, the mil fill is now an inspection/clean out port.
So I am looking for a 800hp capable fuel pump to put in a US Car fuel ring that will get welded to the M932A2 fuel tank. Thinking about a Fleece PowerFlo Lift Pump for an LML. It's 18" long, flows 160gph at 10 PSI, which is what my D-max needs.
I wish it were as cheap as the AC Delco LT4 fuel pumps I use in the gas jobs.
2011-2016 LML Duramax PowerFlo In-tank Lift Pump (Long Bed)
www.fleeceperformance.com
Any one have other ideas?