The economy of 1787 bore no resemblance to the one we had today. A large majority of Americans were small farmers; there were workshops, but no factories; the “working class” consisted largely of apprentices, not laborers; there were no multi-state corporations; and most of the goods that Americans consumed were produced within a few miles of their residence, with the remainder being imported. Large landowners possessed a disproportionate amount of influence, but only in their neighborhoods. There was no need for antitrust law.
What would the FFs say about antitrust under today’s conditions? Hamilton was essentially an 18th century Whig, so you can imagine him supporting big business, subject to reasonable regulation by the state. Jefferson and his followers envisioned an America run by yeomen farmers and small businessmen. They opposed governmental intervention in the economy in their day, but under today’s very different conditions, you have to think they would be strong champions of the use of antitrust law against huge corporations, because the government is responsible to the voting public, while the corporations answer primarily to their wealthy owners.