I would say wait for an SCT tuner to come to your area and just get that, it is much better than a mail order chip. The guy that makes FordChip also does the SCT tunes.
I am going to change my transmission fuild in my 3650 soon, but I can't seem to find Havoline around here anywhere, Would Valvoline Dexron III/Mercon ATF be find?
Looks good, one thing I would suggest is get a full catback instead of just weld in muffers.
You could always ditch the SpeeCal and timing adjuster, then use that money on a custom chip which could do the same thing and more.
I lived through an Indiana winter driving a 2000 V6 Mustang, no ABS or Traction control. I bet having a GT 5 spd would be better since it has trac-lok just make sure you get the ABS option, it is no longer standard. I don't drive my GT in the winter since I have a beater and my tires aren't...
With 3.73 you would be at 80 mph at 2750rpms in OD
With 3.55 you would be at 84.5 mph at 2750rpms in OD.
With 3.27 you would be at 92 mph at 2750rpms in OD.
Edited to change numbers to Auto
There are whole new replacement headlights that you can find on ebay with clear corners, I would get those instead of taking your current ones and cutting the side markers out, it looks ok from a distance, but upclose it just doesn't look clean.
I like my Bullitt Knob, but MGWltd.com has some nice ones, their GRIPPER shift knob feels really nice. My bullitt knob fits too well to mess with getting a new one, but if I did I would get an MGW.