Various combinations to achieve 2.1 and 2.35 engines, rod length crank stroke, piston height, bore size and so on. Cost effective stoker engines are 2.1 which uses the 2lt block, the 2.35 however can be achieved in to ways. The first and foremost the strongest would use the Ej22 closed deck, and second would use the ej257 which in fact is destroked to achieve the 2.33 by using the 75 mm crank from that of a 2lt so not technically a stroker engine, all of the above use custom rod and piston combo’s.
The main benefits are increased toque and better revving engines.