The spark plug pix?
The bottom one can be found in any 2004-2007 F150 with a 5.4L.
The top one is for a 2008+ F150 5.4L with the newly revised head.
To answer your exhaust question.
Don't cut the "y" and you'll be ok.
The "y" comes down from the heads and has the cats and O2 sensors and then merges. Go alittle bit farther back and then its the catback connection point.
There is some stuff you can do to the "y" without getting retuned but since you are only looking at catbacks I'll stop.
Peace!
