I just checked a '68 250 head and it's bolted this way starting from middle of head out:
2 Bolts 1 3/8"
2 Threaded Studs 1 1/4"
2 Bolts 2 1/2"
2 Guide Pins
There were no washers used. The differences in stud and bolt lengths is to provide manifold
and wrench clearences when bolting them up to the head. You probably knew that any way. You can use studs if you like. It makes it easier to
keep the gaskets in place and to support the manifolds in the bolt on process, just use the correct lengths.
