I'm not sure, I only had a 20psi guage when I started putting the car together 30-35psi is my guess.....
if you decide to keep the mustang replace the fuel pump before you do much driving
scott it already has an mls gasket and head studs, the valve cover gasket is probably O.E. make sure you get one from ford all the other gaskets are junk
I would not go five lug on that car unless you can't find a four lug wheel you like just upgrade to four lug v-8 brakes the car is so light it really doesn't take much to stop it