I noticed that most do not include changing lifters when they change cams, springs, and pushrods. Why arent the lifters being changed? Is it a mileage issue?

 

I think it has to do with the extra work involved. You have to remove the intake manifold and heads to get access to them.

Also, the stockers seems to perform relatively well. I know I wouldnt go through all the work for a zero performance gain. I have not heard of too many lifter going bad either.

 

Unless you go with a very aggressive cam, the stock lifters are fine.

 

You don't need to change these lifters like you used to have to do with the old school SBC because we use roller lifters verses the flat tappets.
Roller lifters do not wear and create a pattern that matches the cam like the flat tappets did. This is why nobody really replaces them anymore because they had virtual no wear on them.
The only time you may want to replace them is if you have a lot of miles 100+, they are worn, or you have a very aggressive cam.

 

Not to mention that on GENIII engines, you have to pull the heads to change the lifters.