Two principal questions are treated: (i) Which equilibrium conditions (or, which types of factor demand equations) based on the neoclassical single-capital-good model are unchanged when there are many different capital goods, only one of which is used at any one time? (ii) Are there any "pseudo" productions functions (of "capital" and labor) which correctly describe behavior by profit-rate maximizing entrepreneurs in the many-capital-goods model? A new surrogate production model is developed to resolve these questions. It is shown, inter alia, that if one wishes to predict changes in labor and value capital requirements in response to changes in factor prices, the neoclassical marginal rate of substitution relationship can be justified as the basis for the econometric specification.