[Tom]

Your all assuming she needs a tune up. She said it runs great no issues, so lets skip telling her to buy spark plugs. Although for only $800 I get where you guys are coming from.

Long tube headers are a good upgrade for low bucks.
Aftermarket carb won't get you any more power.
Camshaft would be my next step, if you can handle that kind of work. Otherwise, its alot of money to pay someone to install.
Intake manifolds are cheap

In the end, more power cost a lot of money. Being on a budget, you don't have a ton of options. Most upgrades will cost as much as you paid for the truck or more if someone is installing for you.