Happy 21st man! I have mine coming up in just under 6 weeks
If you want a 12-13 second car I would say that goal will be easier to achieve with a cam instead of rockers. But if you do rockers 1.9 ratio is what you would probably want along with some oil restricted pushrods. Rockers may give you 30hp in the upper rpms while a cam might give you 50hp across a much broader rpm band.
When it comes to the valve springs I would say go with the comp cam 105’* they cost a little more but supposedly they are easier on the timing chain. And they probably would take more abuse since they are a heavier spring.
An intercooler is not much of a power adder in itself. It helps you rid your car of any KR it has then you can increase boost and/or timing.
As for pulleys it is always best to scan so you know what size you can run with your setup.
I wouldn’t recommend pacesetter headers to anyone. & with that being said I think 1 or 2 have installed them on a H-body but I’m not sure what needed to be modified in order to make them fit.
If I may suggest a route to take your mods I would say get some headers (SLPs or TOGs.) And then decide if you want rockers or a cam.
1998 SSEi The Executive Hauler
Built Trans w/ 3.29s, P&P Jenny 5, S1X cam, Silver TOGs, Northstar TB & LQ4 MAF, FWI, Dyno tuned, #60 injectors,Oil Pressure Kit, 2.9-3.4MPS, MagnaFlow exhaust, 3" HF cat, MSD Coils & 8.5mm Super Conductors, AeroForce, only Sunoco 94, 100