I have a 1951 Pontiac Chieftain with a straight 8 engine. When I bought it the Cylinder Head was loose and the bolts are nowhere to be found. Can anyone tell me the specifications for the bolts? Length, Width, Thread size, type of bolt, etc.???

I also need to know if I should re-tap the bolt holes and what kind of lubrication is recommended when I screw in the new bolts. Any help is appreciated.

I'm not sure about the type of bolts. But if the head bolts protrude into the engine block water jacket, then the threads will need to be treated with sealant. Most of todays head bolts already come pretreated anyway.

Even if you get the answer of what should be there from us or elsewhere on the Internet, you might want to take it to a machine shop so they can tell you for sure. In 70 years it'* possible someone worked on the engine and to re-tap them at one time or another.