Be advised that header wrap seriously promotes corrosion.....and almost all header manufacturers will NOT honor their warranty if wrap is used on their product.
If you are planning on wrapping them to reduce engine compartment temps then look into coating them with ceramics. It might not work as well but it WILL be cheaper in the long run since you wont have to replace the headers often.
Header wrap only promotes corrosion if it gets wet all the time. I wrapped a header for a '91 Civic and the header didnt have ANY rust after two years. It also stays alot drier here in CA.
The header was out of the car and I cut strips longer than I thought I needed. Then I secured them with hose clamps. I only wrapped the header because the A/C lines came really close to it. I wouldn't do it for fun.
I almost bought header wrap for my headers when I asked pertronix and a couple other places about whether or not it voided their warrenty. well guess what..........IT DID. Jet hot ceramic coatings is probably the best place to get ur headers ceramic coated. Even though their price is high, they strip down any paint, and coat the headers on the inside and outside. they also do some stuff in between but I forgot