02 ls1
The only way to know for sure is to measure the piston to valve clearance. I have seen some threads where guys have had success jamming the cam in and others say the pistons had valve contact marks after running the T-Rex. Since there are several variables at play (have heads been milled, etc.) it's always best to check. If you do end up fly-cutting I think you can go .080" safely on stock pistons but maybe someone else can chime in and provide some more clarification.
https://ls1tech.com/forums/generatio...treet-car.html
Also make sure to use a high quality spring kit like the btr .660 kit. i would not chance it on used springs with unknown pressure.
That being said, most of the time it fits with all stock heads, gaskets.





