Could someone outline the main differences in performance and reliability between the 289, 302, and 390 engines from the 67 to 68 mustangs? I know the horsepower for each engine, but how do they compare to each other? Is one engine recommended over another?

 

Consider the 289 and 302 to be the same engine. Only the crank and connecting rods are different. I've never owned a 390, but the 289/302 is a great engine for daily drivers or occasionally driven car. Lots of bolton goodies, they're inexpensive, good reliability with no real troublespots, decent gas mileage. They get my recommendation.

 

289/302 SB: There are a ton of aftermarket parts for the 289/302, it's relatively light weight, easy to get around and maintain under the hood, better gas mileage if it's tuned right, better handling car with factory suspension, cheaper to get into initially and probably cheaper overall.

390/FE BB: Lots more torque, variety of aftermarket parts not as great ( ), more torque, heavy weight affects handling, more torque, not much room to change plugs, more hp & torque... oh, and did I mention more torque? B)

There's a trend developing here. You can get more hp and torque out of big block than a small block - period. But you're going to pay for it.

Reliability? Depends on how the engine was maintained before and after you got it, and how you drive it. I don't think reliability is really a question. Given a reputable machine shop rebuild, I wouldn't think there is much of a difference.