Dan, here's a 1971 Skylark factory hitch. 1970-72 differed a bit. Like a 1972 hitch had a longer tongue because of the rubber inserts on the bumper. There were different classes of hitches, too.
I used one of those clamp ons to tow my buddies 61 Chevrolet Impala convertable to Englishtown drag strip in the mid 70s so he could race . I towed it with a 68 GS400 and then raced the Buick in I think F/stock only because I had snow tires on it and I couldn’t run pure stock . I raced with the tow hitch and chains on , it probably added 100 lbs.
My old GSX was used from new or nearly new to tow/launch a boat. Rack for water skis dented the roof pretty good. I towed a open car trailer for years w/my '69 Sportwagon 400. Class III Receiver hitch welded on. Probably way more weight than the car was rated for. Never any trouble. My 2nd '69 SW (purchased from orig. owner in '94) had a class II type hitch installed when I got it. I currently have a '70 Skylark that has the requisite holes in the trunk floor so it used to tow something. I recently sold a factory style class II hitch to a guy who was using it to tow w/his '71 GS w/N25. I cringed a bit until he told me the car had a hitch before he owned it & the holes were already there. He was happy to find a hitch that lined up w/those holes. But the best one is my '70 GS 350 4-sp. Very low option but was factory equipped w/H1 (Trailer Towing Suspension). On a GS 350 w/manual transmission, this also required G1 (performance axle w/positive traction - 3.42) which was then upgraded as a SCO to 3.64 @ no additional charge. The posi part was req. because there was no 3.64 open rear made. However I don't believe the car was ordered for or ever towed a trailer but interesting "factory tow car" related trivia. In '68-9 the requirement was a 3.91 which remained in '70 for Skylark even though a Skylark could be ordered w/a high-comp. GS engine. So if you ever run across a '68-70 Skylark/GS w/a manual trans, there's always a slim possibility it has a rare/valuable rear axle assy.
