whats better for the top end?..slp runners or headers?

 

Is the LB9 the 305? If yes, I would buy the large tube runners, and do some porting to the plenum and base. With the factory heads, I would just port the exhaust manifolds until I could get aluminum heads, then go with 1-5/8 tubular headers.

To answer your question directly, I have to say both. You got to get more air in, and you got to get it out! Sorry I am not of more help.

 

I would say exhaust first if you have to choose.

 

definitely headers...

 

The right side exhaust manifold narrows down to 1 inch inside diameter right ath the back where it bends down to got to the wye pipe. There is nothing you can do to open it up. Go with exhaust upgrades first.