Yer the garrett is internal, is this for a gtr? so twins? or just single?,,,the 2860 -7,-5,-10 turbos and yes there in that order smallest to largest there a turbo made by garrett for the gtrs they have the t25 flanges so there a direct bolt on to the stock manifold..as for the diff between internal and external waste gates im still fairly noobish but as far as i know an internal gated turbo has an inbuilt waste gate and actuator on the turbo, a external gated turbo the waste gate is fitted to the manifold as apose to being on the turbo it self, as for the fitting for an external gate if its for a single set up youll need a custom manifold with a tial vband for the waste gate the be placed your better off talking to 6boost about this stuff because its there bread and butter and i have yet see a better made manifold youll find them in the buisness section