ok I'm new to this and this is my first motor build. I'm looking to buy new roller rockers and I see there are stainless and aluminum. What is the big difference between the too?

 

In theory, the stainless rockers have greater fatigue life and therefore are preferred for the street. That said, many people (myself included) use Al rockers on the street with no issues. And GM used them on the LT4 from the factory. I prefer aluminum due to the lighter weight.

You need to be careful what you are buying and decide if you want self-aligning rockers, which do not use guide plates or NSA which require guide plates. Many people prefer guide plates for more extreme cam profiles/higher rpm. If you decide to use guide plates, be sure to buy hardened pushrods. If you decide on Al rockers, be sure to get the slightly narrower ones designed to fit heads with center bolt valve covers.

Rich