I have a 1990 f150 with a 351w that has just over 300k on it and I'm wanting to get a little more power out of it to help tow and turn the 35x12.50 15lt tires, any suggestions? On a student budget so $1000-$2000.

 

I am assuming the engine is in good mechanical condition, and can support a little more HP and Torque. 300K is a lot of miles. The best way to get more power from a factory Ford is to improve it's breathing. For the budget you are talking about, you should be able to buy a decent set of aftermarket aluminum heads with bigger valves and smaller combustion chambers (if you do the work yourself). This, along with a set of headers will make your Ford breath much better, and raise the compression, if you get smaller combustion chambers. I am sure there are other options, but this is where I would start.

 

What axle ratio does it have? Anything less than 4.10 is fighting an up hill battle you won't win. The next best upgrade after gears is a cam swap, new heads are almost a complete waste of money until the factory cam is changed... it really is that bad.

 

heck with 35's you should run at least 4.56 gears. motor upgrades will cost way more to get you moving in a decent manner.