[427sharpe]

Actually, one of the most important things in determining strength is the pinion ratio or how high or low the pinion rides on the ring gear. This is what makes the 9" so strong...and also what makes it soak horsepower. As for durability, there is a reason why the 9" is still the top rear end...BRUTE STRENGTH and balls on reliability. NASCAR anyone? Still using 9" rearends basically lifted from a '65 Galaxie (layout) and still never breaking one. Gearsets are still plentiful and reasonably priced and the diff is very easy to set up. Not bad for a rear end that last saw a production line over 20 years ago. I would say if a solid axle is the choice and you want reliabilty behind a lot of torque and in front of slicks, the 9 is the way to go. If you are a cruiser that will see ocassional track, the 8.8. In IRS, I have built a number of setups for all kinds of cars, and the 8.8 has been excellent. In a Cobra, I would say that the differential mounting would be the most imnportant factor, as the TBird diff has relatively weak mountings. If you go the 8.8 road, use an Explorer diff and axles, as they are much stouter than TBird/Cougar/Mk VIII. A big plus, parts are readily available anywhere, and practically any full service garage can fix a problem...can't be said of Jag stuff.