B18C1 block will bolt right up. You don't even need to do any extra work like you would if you were trying yo bolt up a B18B block. Just yank the B16 block, and replace it with the B18C1 block. The LS crank and rods in a GSR block has been done before, and yields the longer stroke and added torque of the B18B, with the reliability of having pre-existing VTEC oiling components and girdle. Basically all the advantages of an LS/VTEC without the reliability issues.