97 Cobra ball joints

The 03/04 Cobra A arm is the same A arm with a revised 99+ ball joint and a set of stiffer bushings. As far as I know there is no physical difference in the A arm itself.

Is your car lowered ? If it is, then I suguest these:
http://store.summitracing.com/partdetail.asp?part=FMS-M-3050-S&FROM=MG

If not then just use stock parts or use those and you can lower your front end 1/2 an inch.

There is a tool to do this service without removing the A arm from the car. It looks like this:
http://cgi.ebay.com/ebaymotors/BALL...010QQitemZ200151642603QQrdZ1QQsspagenameZWDVW

I would recomend yanking the coil springs just for safety when you are doing this.