An additive manufactured heat exchanger includes a monolithic housing defining an outer surface, a plurality of first fluid passageways extending between a first fluid inlet and a first fluid outlet, and a plurality of second fluid passageways extending between a second fluid inlet and a second fluid outlet. A cross section of the outer surface defines an irregular shape, the plurality of first fluid passageways and the plurality of second fluid passageways define a convoluted flow matrix within the monolithic housing, and the outer surface of the monolithic housing is complimentary to a space between at least two components of a vehicle. The monolithic housing can also include a plurality of third fluid passageways extending between a third fluid inlet and a third fluid outlet.