While working on the them the same time use a box to keep 89 and 90 apart. and baggies labled 89 and 90 for piston, rings, pin, bearing ect.. So during testing not to get confused. if the 90 is sealed and 89 is unsealed you know what your working with. been there and done it. please mark cylinder with marker 89 or 90. head no worry diff color.