1992 Ford Econoline repair advice needed

A neighbor owned this Ford van. It failed inspection and he was going to junk it. I outbid the junkyard, so now it is mine. I hope to do the necessary repairs myself.
The first and most important task is to correct a prominent exhaust leak. That's the principal reason for failing inspection.
The engine is a 300 cubic inch straight-6. It has two exhaust manifolds, one for cylinders 1-3 and another for cylinders 4-6. Using a length of rubber hose as a listening tube points to leakage at the front end of the rear manifold (at cylinder 4).
I want to remove the manifolds (one intake, two exhaust) to replace the gasket. Rusty fasteners will be a problem and a broken stud could be a nightmare. I'm proceeding slowly and carefully, using liberal quantities of a liquid penetrant product.
I have no prior experience working on this engine. If it were in an F-150 this repair procedure would be easier. In a van, see-and-reach are seriously limited.
I have not been able to put my hands on a manual, and am resorting to this forum. Please... someone who owns the manual or has done this job... give advice. Is it necessary to remove the alternator? Remove the large cast aluminum fixture which supports the alternator? Does the top of the two-piece intake manifold remain in the engine compartment or should it be removed? What pitfalls should I watch for?
Thanks for guidance and wisdom!
Daniel B. Martin
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