With my engineering background, I'd recommend all your contemplated mods and in addition, add a Tornado and HHO, but be sure to put the HHO outlet
in front of the Tornado or it won't work. Also, you will only get piddle around results if you only piddle around, so forget the glasspack and go straight pipe. Straight dual pipes, exiting ahead of the rear wheels to avoid that restrictive over-the-axle hump. Pull that restrictive catalytic converter outta there while you're at it. Then put some Monster Mudders on it; these will do several things: they'll give a much desired gearing up, and they will get the body and chassis up and out of the dense layer of air that exists in close proximity to the ground. A lift kit will only improve it further.
Other must-have aero tweaks are fender flares (to guide air away from the wheelwells), air tabs (to promote the turbulent wake zone), and air deflectors for the hood and front doors.
Acetone must also be used but be careful, too much or too little will fail to give the promised results. I'd suggest using acetone only for every other tank, and alternate the acetone treatments with a fuel line magnet. DO NOT USE THEM BOTH AT THE SAME TIME!!!
On that note, once you achieve good cold air intake temps, you will then need the hottest fuel temps possible for better vaporization and atomization. Google the net; there are many fine plans for copper tube fuel line heat exchangers that the handy and clever can fab up at home for nominal cost.
I should add that those mods might move the BSFC curve upwards and the best economy is found in the meat of the BS FC band, so you may have to go 80 mph instead of 65-70 for best economy.
Good luck!
