I broke three bolts when removing the exhaust manifold to install the header that I got from Terry. After soaking them again for another 48 hours with PB Blaster I welded a nut to the stud and they broke again. After getting the bolts cherry red with a torch and using a stud remover they broke. I decided to remove the head and drill out the broken bolts. The worn out rockers and shaft was almost as stubborn as the exhaust manifold to remove. When Terry called to ask me how the header is going I explained the problem with the bolts and he said come get the head that the header was attached to. The head was from an ‘80 Mustang that was rebuilt less than 2000 miles ago and was milled .070 to make the compression ratio closer to 9.2 using today's thicker replacement head gasket, whereas the factory had it around 8.0. It also had a new rocker shaft and rockers installed along with stainless steel exhaust valves. Terry also gave me a new gasket kit to install the head. Since the head has been sitting for a few years I went ahead and replaced the valve seals before installing the head on my Maverick.
Couple good things about stepping up to a later model head other than having harden valve seats is the bigger intake valves, 1.75" verses 1.65" and larger intake log, 1345 cc verses 1240 cc. I know these numbers don't sound like much but the way I understand it, with a six cylinder it's enough to make a difference because it is easy to go too big and keep the street ability. I'm not trying to make stupid horsepower because I will need to feed these horses.
I decided to replace the non-adjustable rocker shaft with the pre '64 adjustable rockers since the shaved head was pushing the limit on the factory length pushrods. This required 1/4" shorter Ball/Cup style pushrod to be used. I did have to go back and add a little more clearance on the valve cover baffle. I also used harden washers under the head bolts to keep the bolts from bottoming out and help spread the load. I had to go back and add a little extra clearance to the baffle in the valve cover.