18R-G
4A-GE 16v
4A-GE 20v (pushing it for budget)
3S-GE (again with the budget)
CA18DE (not sure on prices, but these would have to be pretty cheap right?)
SR20DE (probably over budget)
12A atmo
13B atmo? (not sure about the legalities of this one, or if the price would be prohibitive)
Bare in mind I've no idea how easy or well any of these would fit, they're just all smallish rwd non turbo engines. A budget of $3000 will make any conversion difficult, unless you're doing pretty much everything your self.