Which rear end is it, the 8", or the 8.8" ?? If it's the 8.8", there are almost as many gear ratios to select from as there is for a 9", if it is the more common 8", you will be a bit more limited. The handling should be fine as long as you size the spring rates to correspond with the car weight. Plan on using coilovers, or the stock Cougar pieces???