If you are on a really tight budget, then you probably aren't going to buy new heads--which is where a lot of power is hiding. You can still easily reach your intended power level by upgrading to a new intake/carb, nice cam--but don't get crazy here, and be sure you have a good dual exhaust system.
Do not put a big cam in this engine. You will kill the low end torque, and the heads won't let it work at the higher rpm's. Too much cam is about the only way you can screw up. Stick with a cam with a .05 duratiion of 225 degrees or less. You should probably use one with about 215 or 220 degrees with the stock heads.
Clark made an excellent point here--if your not sure what your doing, call someone like Edelbrock or Holley and they will give you matching part numbers for a cam and an intake that will work well together and with the heads you use--be it stock or aftermarket.
Make sure the intake you buy is a dual plane, and realistically, you can use a 600 or 650 cfm carb. on it.
If you have any money left, buy some rear gears. If you have 2.75 or 3.00 gears, just moving up to a set of 3.55's will make a bigger change than anything you are going to do to the engine.
enjoy, 351's can make a lot of torque and destroy a set of tires.
[This message has been edited by 66fastback (edited 06-08-99).]