I used cooper and they work well
However the remflex gaskets work waaaay better.
The first set of tmh I did I used the supplied gaskets that was in like 2005
I have never used the supplies gaskets again because they won’t seal up and blow out
This is not a job you want to do over and over
There are
Several
Ports where the only access to the fastener is with a wrench and you must tighten the header to the head evenly otherwise the bolts will be too long to get wrench on
I have a set of special
Tools I use for this and I have some special header Bolts I use as well
I shaved a socket down to be very shallow and I cut a wrench in half so I can use the box end with a small cheater pipe
I have installed about 5-10 sets of these headers
The modifications I've made are high flow water pump and thermostat which made a big difference along with the twin electric fans. But I want to put dual exhaust after the cats. I don't seem to find anything. I guess it's a custom make. I do have the Gibson currently which is definitely better than stock.
They are gaskets with metal in the middle