Ok I'm going to be putting in LT's soon and I got my gaskets yesterday
I ordered The percys ones.
This is a dumb question but, I'm not sure what way they go on one side is flat and the otherside
is kind of curved, so witch side mates on the head and what side goes onto the header?

Thanks in advance

 

Kinda curved? I'm not familiar with the Percy's.

 

I doubt the slight curvature matters, my Fel-Pros were slightly curved when I took them out of the packaging. They will be sent back to shape once the headers are installed and the bolts tightened. I installed the flat side of the gaskets onto the head portion and they sealed perfectly.