Chevrolet Cosworth Vega.
110hp, EFI, DOHC in a fairly compact, lightweight, package. It's a rarity, and an enjoyable little bugger. Kinda like an american Hachiroku, only far less famous. Oh, and it was built in 1975-1976, so it's become a collector car. that means the value appreciates with time, provided you don't run it into the ground.
It's very much like one of those older Nissans you suggested. Rust is a problem with Vegas, watch out for it. (though, suprisingly, most of the Cossies still exist, with only a few major rust problems. did they do something different?)
The star of the show is the Coswoth Twin Cam engine. The EFI system seems to work well on these, but I'm pretty sure a popular alternative setup involves two Webers. It's probably a bit more reliable: I'd be wary of early EFI systems. Probably also improves horsepower by leaps and bounds, too, given restricted intakes of the day. My father knew a guy who must've had at LEAST 240 hp in his...it was scary-fast!
I'd reccommend you look at that one as an alternative to your older Nissan/Datsuns. The price: usually under Ten Grand.