Fragments of glazed pots and clay pipes were also among the finds, which date from the 14th to the 17th centuries.
More precise dating of the artefacts is under way, with the remains of four medieval structures where the objects were found believed to be from the 10th or 11th centuries.
They are thought to have lain undisturbed, a foot below the motorway’s southbound hard shoulder, because of a nearby religious site.
The discoveries were made last autumn during road widening work at the site, beside the River Clyde and Strathclyde Park, opposite Hamilton services. The village was cleared by the Duke of Hamilton around 1445 to give himself a clearer view. It was moved one mile south to what is now Hamilton.
A total of 400 pieces have been unearthed, including 240 fragments of pottery dating back to the 14th century.
Guard Archaeology, which led the work, said the scale of the finds was extremely rare.
The lead shot may have come from the Battle of Bothwell Bridge, half a mile away, when government troops defeated Presbyterian Covenanters in 1689. It could have come from an officer taking shelter in the then village ruins.
A horseshoe found could have come from the battle too.
Another discovery was a spindle whorl – a stone ring which acted as a pendulum to tease out yarn for spinning.
Project manager Warren Bailie said: “Assembling all the objects will enable us to reconstruct how people lived.
“Medieval remains rarely survive in industrial centres such as Glasgow due to widespread industrialisation of the 19th century, including mining and road and housing construction.
“Very few medieval settlements have survived, so we’re delighted to recover and record such a rare piece of Scottish history. There are no plans for further excavations, but if there were, I don’t doubt we would find more.”
Mr Bailie said Cadzow was settled at a crossroads and ferry crossing of the Clyde, close to the then main Edinburgh-Hamilton road.
Infrastructure secretary Keith Brown, who viewed the finds yesterday, said: “The discoveries, which could have remained uncovered had works not started, are truly remarkable and underline the value we place on meeting our environmental obligations as we plan and construct essential new infrastructure.”