Can and will share the size and thickness of the materials that I used.
To start with all receiver sockets that you see are just that you can buy them in 6" and 12" lengths they are for the 2" class III hitches.
the 2" square tubing may be a little hard to find since it was 5/16" thick also a size commonly used in the actual receiver ball mounts.
the tubing used to make the body for the sliding inserts was 2 1/2" by 3/16" thick the gussets used were made from ASTM 514 T1 because that is what I like to use a lot A36 mild steel would work just fine though the clamp plates and the bolting boss plates are all 5/8" thick ASTM 514 T1 yes these could be substituted with a lessor grade of material ASTM GR 70 or 50 or even A36 mild steel if that is all that can be had. all welding was done with 1/8 and 5/32" 8018 and all parts were heated to at least 400°f prior to welding I did not have a power sourse for my mig welder at the time or I would have welded it up with .045 Essab duel shield flux cored wire. I would not feel comfortable in ever telling someone to weld any structural member with gasless wire or solid bare wire unless it were .035 or greater with 75/25 Argon/ CO2 mix gas or 98/2 Argon/ Oxygen or triliene mix gas with at least a 250 amp machine.
Could this have been welded with 7018? yes but if T1 steel is used it is at the marginal low side unless the welder has good experience. It is very tempting for a novice or a welder with little experience welding alloy metals to either run too cold or too hot with all filler materials.
I usually recommend that a welder should always make several test welds of scrap make some butt welds always beveling the weld area to a "V" make some lap welds 1 side only make some inside and outside corner welds then try and destroy them in a vice with a hammer or in a hydraulic press most guys have the capability do do one of these milling a coupon for a tensile test is usually beyond their means and usually not necessary sawing a nick in a fillet weld and placing the piece in a hydraulic press on edge will serve much the same purpose.
All holes were threads to 5/8-11 to give you the bolt size
I sincerely hope this helps should you decide to make one for your own And for anyone who may be considering making one or any of the things that I have made and posted remember I have no control over your skill set level nor can I dictate the materials you use. Your skills and dedication to making things are purely your responsibilities and my recommendations should not be taken as the all seeing all knowing way things should be done. My stamp is retired