What is the correct diameters of them for a stock lt1?

 

3/8 screw in are stock. You can upgrade to 7/16 without any issues or machine work. The impala SS iron heads however arent screw in and interchangable without work.

 

The actually part that screws into the head is 7/16" but then tapers into a 3/8" so the 3/8RR will fit. I'm just double checking.

 

The studs are 7/16 where they thread into the head and 3/8 on the top stock. I went with 7/16 on the top with mine, since I was replacing getting new rockers and studs at the same time. As long as the two sizes (stud and rocker) match, it doesn't really matter. The 7/16 should be stronger, but I doubt I really need it. It was just a case where I could get stronger parts for the same money.

 

Thanks for the reassurance!