Please excuse my bluntness here, I like that you have an interest in modifying, that's always good.
But Sunbirds are not worth any money put into them. There is no resale value to one, no demand for one, no want for one, and 99% percent of the world thinks of them as total rubbish. Save your $6k, and buy something that's actually worth putting your money into. S13, S14, Miata, RX-7, older Celica, MR-2, Mustang, Camaro, Firebird, Corvette, 300ZX, etc. Hell even a Civic, S2000 or VW GTI are so much better of a platform. After you spend all your money on it, you're still going to be left with a car that doesn't go real well, doesn't stop real well, doesn't turn well, doesn't pull chicks real well, doesn't look real good, but gets you to work and back on time.
And how is that any different than how it sits now?
My advice would be fix what you need to, to keep it mechanically alright as a DD, and buy a project that will actually allow you to meet your goals