Listen to what has been said- some very good advice. I have a 90 lx convert that I bought bone stock except for flowmasters and a
K&N cone filter a few years back. It was ...................slow. I mean really slow. Mid 15 second slow.
Now, before you do anything determine what your goal, budget , and use is. Is this a DD, weekend or 2nd car?
Once you figure that out here is what I recommend doing in order- some of it is redundant to what has been said.
Regardless of what you do from here- address the Safety, brakes and
suspension- go to maximum motorsports and read their tech pages. One of the best sites to learn about this and their tech guys are great. Yes, I use and recommend their parts as they are the best on the market and are US made.
Maximum Motorsports full length subframe connectors
Check the torque boxes- if they need attention - wild rides boxes
Replace worn sway bar, end link, front control arm bushings with quality poly ones
Repace motor mounts, trans mount with new OEM or poly
Quality shocks and springs- depends on what your goal is. DD? stick with the stock springs if not worn and a good replacement Monroe shock.
If lowering or a street/strip/weekend car, Steeda or H&R springs and some Tokico or Bilstein shocks.
If you want to spend the money, a good coilover setup;
Rear
control arms- DD stick with stock ones with new oem bushings. If you want an upgrade. MM rear lowers and new stock 94-95 uppers.
Brakes-
if keeping the stock 4 lug drums. Again , MM sells a great upgrade kit with Hawk pads, shoes, stainless steel caliper bushings and stainless steel brake lines. Huge improvement over stock. Get a good set of OEM replacement rotors and drums from Rock Auto. No need for drilled or slotted rotors.
If going rear disc or 5 lug check the tech archive as that is a topic on its own.
Cooling-
stock- stock copper radiator and OEM fan
upgrade- good 2 core aluminum radiator and an electric fan
Charging- replace the stock alternator with a newer 3g 130 amp alternator and upgraded wiring kit. A must with an E fan
Trans-
get the biggest plate style trans cooler that will fit . I use a B&M mounted in front of my condensor.
Valve Body- call Dan at Silverfox and get one of his valve bodies.
For engine mods, you essentialy have a few choices- naturally aspirated or a power added
Naturally Aspirated- get a good set of heads- that is the most important piece of the puzzle. I would recommend either TFS 170 or AFR 165 heads on a stock block 302. For the cam, you will match that to your goal and build. Popular choices are TFS1, TFS2, Anderson N41, Comp Cams extreme cams, and custom cams by Ed Curtis, Buddy Rawls. Your choice of cam will dictate what valve springs on the heads to go with. TFS sells an entire top end kit for about $2800 that is popular and normally nets around 280-310 rwhp. Whatever you do, avoid the Ford alphabet cams. they are 25 year old technology.
Power Adder- you can do turbo , blower or nitrous and add anywhere from 50-125 hp on a stock motor safely. Nitrous will cost around 700-1000 but then you have to keep filling bottles. A good turbo or blower is around 2-3 grand.
Exhaust- I don't care if LT headers add 20 hp, on a street car don't do it. You will curse them every time you need to get to the starter, trans or if your car is lowered.
Obviously, when you start adding power, you will need to upgrade other areas like cooling, fuel delivery, brakes, etc. and it all can't be covered in one post. Take a look at my profile to see what I've added to my car. It has around 300 rwhp. You can find a lot of used go fast parts to help save money.
Edit:just saw your post. With a budget of only 2500 the only way you are getting near 300 rwhp on an AOD is either a carefully matched top end kit or a power adder- and that is buying them used. Along with that you will need to upgrade your MAF, injectors, throttle body. fuel pump, exhaust, valve body or shift kit, and with an AOD you WILL need a tune that is another few hundred.