My $0.02,
1) I'd chase the threads in the head with a tap to make sure the threads are clean. Depending on the age/condition of the bolts, I'd possibly replace the manifold bolts. I'd also thoroughly apply anti-seize to the bolt, all the way up to the bolt head.
For a cast iron exhaust manifold: If the surface on the cylinder head is true and straight, you can have the manifolds mating surface machined flat and leave off the head to exhaust manifold gasket. You have to be sure the head and the exhaust manifold are both true, otherwise use a gasket. For the exhaust pipe studs on your manifold, when the manifold is already off is the best time to replace those. It will likely require heating the manifold with at torch, or sometimes just burning the steel studs out of the cast iron manifold. Whether or not you replace the studs, I'd liberally coat those with anti-seize as well.
2) Will the rams horn clear the crossmember? If I was cutting cast iron, I'd use a cutoff saw with a blade that can be used on cast iron or a hacksaw and clean up with a grinder or file.
3) I typically will use a thin layer (i.e., very thinly spread) of something like Permatex #2 on paper gaskets such as water pump, fuel pump and thermostat housing gaskets and sometimes cork gaskets. Permatex #2 can also help hold gaskets in place while assembling). For rubber or rubberized cork gaskets, I'd probably install dry. If no gasket or eliminating a gasket (e.g., front and rear of intake manifold- "China Wall" or a transmission PTO cover) then I'd use RTV. Also I'd RTV the corners of some gasket types, like where multi-piece pan gaskets meet the block.
Fel-Pro used to produce a booklet that had some more information about gasket materials and recommended sealers, I haven't seen it or asked for one in a long time though.
1
