Reagan wasn't entirely wedded to conservatism. Calvin Coolidge wasn't either as seen in his later speeches and spending as the economy recovered from deep and immediate cuts. If the had been Constitutionalists, Reagan would have cut deeper to the point that he defunded big govt cronies. If Coolidge had been a Constitutionalist, he's have ended the Federal Reserve.
Both Reagan and Coolidge (Harding too) didn't slam the barn door and hence lead to massive future expansion of government. If they had truly espoused limited government, America would have another 100 years of prosperity and FAR less cronyism.