While Mattick argued that debt financing would compound capital's crisis tendency in the long run, he certainly was not an apologist for the free market (while Hayek seems to have eschewed the concept of equilibrium, his exogeneous monetary theory of the crisis cycle was certainly rejected by Mattick) or an enthusiast for the return to the gold standard or the operation of a simple money rule. I would imagine however that while Friedman must have appeared to Mattick as a laughable prize fighter for the bourgeoisie (see Geoffrey Pilling's comments on Friedman in his Critique of Keynesian Economics--a Marxist View), Hayek's Counter-Revolution in Science would have been welcomed for its critique of technocratic socialism. Mattick was a fierce critic of Bolshevism.
I would like to make an unrelated comment here on Marx's empiricism. It would be interesting to figure out why Marx held Richard Jones who had intensively studied historical differences in the economic systems of India and Britain in much higher esteem than the abstract and deductive theorist Ricardo. There is also an essay in defense of Marx's "redoubled empiricism" by Patrick Murray in the latest volume on Marx's method edited by Fred Moseley and Martha Campbell. Will have to reread that as well.
> So did Hayek and Friedman, didn't they?