Believe you are correct that the 3 groove pulley you claim will work - will work. The difference between the pulley you show and the pulley they show is that your's is a cast pulley and they are talking about a steel pressed pulley. I've come across these cast pulleys on heavy duty truck applications that had air brakes, power steering and generators - that being said what you have is rare compared to the pressed steel versions used on lighter duty - I could be wrong on this because of my age