The LsX series GenIII small blocks are really sort of in between the exterior dimensions of the traditional SBC and the BBC. The Ls1 will accept a 4" crank really easy for 382 CI or if you go with an LQ4/9 block you get 402 with a 4" stroke. The LsX motors bigger than that are resleved blocks with cylinder bores of 4.1" or more. A BBC motor will be huge, the valve covers will be almost wider than your hand and you will know it when you see it.