Mitra's three-body (separable potential) model of stripping is reexamined and new results are derived. In particular it is shown that a DWBA can be formulated for which the DWBA matrix element is identical to the exact stripping matrix element. A similar result is found to hold in the (many-body) case of nuclear reactions if the neutron-proton interaction Vnp is of separable form. The three-body calculations of Reiner and Jaffe are used to show that the conventional DWBA matrix element is a good approximation to the exact (new DWBA) matrix element. The use of a product of two-body wave functions in DWBA to replace the three-body wave-function (neglect of deuteron internal distortion or ``stretching'') is thus justified on the basis of Vnp being well approximated by a separable interaction.Work supported in part by the US Atomic Energy Commission.