A higher gear ratio such as 3.73 or 4.10 will make you accelerate faster because you can get into the power band quicker, but you loose top speed. basically 0-60 is faster, but top speed drops from about 135 to 115 without the govenor of course. City MPG will go up very slightly because you can accelerate quicker and stay low rpms, but highway will go down slightly because instead of being at say 2000rpms, you'll be closer to 3000 rpms in 4th gear. And just FYI, if you go with a higher gear ratio and get it dyno'd to see how much power you have, the readings will come out lower because the hp cannot catch up with the acceleration. It's weird but true. I personally would go with intake and exhaust first, which ever you do first is your choice. It'll change the sound and get some more power, plus it'll alow for more power later on if you keep upgrading.
Tlok or a limited slip differential will allow the car to grip better. With the open differential, the right tire will slip and it will try to put power on the right so you don't move. With an LSD, it'll shift power equally and maintain traction better. If you stay with just intake, exhaust and gears and maybe a tuner with nothing too high, a ford tlok will hold, but if you go into the engine or bolt a power adder on, say good bye to that. 7.5" Detroit Truetrac will hold up to 350-450 rwhp depending on how the curve is and how hard it's being pressed.
Tlok or a limited slip differential will allow the car to grip better. With the open differential, the right tire will slip and it will try to put power on the right so you don't move. With an LSD, it'll shift power equally and maintain traction better. If you stay with just intake, exhaust and gears and maybe a tuner with nothing too high, a ford tlok will hold, but if you go into the engine or bolt a power adder on, say good bye to that. 7.5" Detroit Truetrac will hold up to 350-450 rwhp depending on how the curve is and how hard it's being pressed.