Here's another good write up for installing headers by dropping the K-member.
http://stangfreak.com/content/index.php?option=com_content&task=view&id=52&Itemid=31
I just put some new Motorcraft plugs in. Those are the ones I'd go with.
Just get a set of these
And get one of these to install them. A plug socket permanently attached to an extension.
You need one gasket for the PS.
Don't know the Ford Part number but it cost around $10 at the Ford dealer if my memory serves me correctly.
Here's what you want.
I just purchased an aftermarket torque converter from West Coast Racing Converters. http://www.westcoastconverters.com/
I wrote an article about them if your interested.
http://stangfreak.com/content/index.php?option=com_content&task=view&id=65&Itemid=1