80-90 roller 360 question

Chuck, I am currently building a 408 from an 89 360. I am using the stock roller setup. When I went to buy new roller lifters the part numbers from 89 to 2004(whenever they stopped production magnums) were all that same. A friend of mine took apart his MP crate motor and the lifters were identical to the ones I am using which are stock pieces. So I wonder why the old engine books say one thing and MP does another.

Steve