If you're concerned about performance, the difference between the Northstar and 4.9 is mainly in the higher speeds. Around town, the 4.9 will keep up with a northstar due to the gobs of low end torque in the 4.9, but above 55 mph, the Northstar will pull away. I have a 4.9 in my '92 Sedan deVille, 111,515 miles and im quite satisfied. Its quite fast, all things considered, and very very reliable. (The only thing i've replaced on my motor so far, was the #5 fuel injector). My 4.9 sprayed coolant once, but that was due to not having the coolant supplement pellets in, after we put those in and poured in a bottle of alumaseal, it never leaked again. Basically, my biggest pet peeve with the 4.9 is the main bearing knock they have on the 91-92 4.9's. This is due to having an undersized #1 main bearing. They fixed this problem mid 1992. I've heard that only the 1991's have it, but my car which was built in April 1992 has it also. So overall, I would have to go with the 4.9. It's a really good motor, with a few drawbacks, and its cheaper to buy, maintain, and is simpler to work on.