Read the 03/04 Cobra FAQ located as a sticky at the top of the SVT Tech sun-forum. It'll amswer many of your questions. We actually have a member here (hotcobra03) who's '03 has 214,000+ miles on it! Yes that's Two Hundred Fourteen Thousand!
Mine just turned 50000 today and the ONLY problem its ever had is a leaking diff cover which they will all do unless you get the diff cover brace. You should do a total system change though. New trans/diff/coolant/oil/SC oil/brake fluid. And the regulars like air/fuel filter. If you have stock rubber bushings chances are a few are worn and cracked in the IRS. Good time to upgrade them
I think mine just ripped its tranny mount cause now I get a clunk when giving it gas after coasting for a few seconds. Other then that they are rock solid cars. Of course the cooling mod is another great idea. I keep putting mine off cause I dread dropping the transmition.
Mine just turned 68,000 miles during this trip to Atlantic City and it will hit 69,000 on the way home. Other than getting a new front case for my T56 because of a bad bearing, I have never had a problem. Other than an MGW shifter, K&N filter and ceramic brake pads, the car is all original right down to the clutch. These cars are tough. Mileage is less important than how the car has been driven.
Ooooops, I lied. I was looking at all my cars reciepts last night and last year it got a new alt. IDK what the stock size is but this is a 165 amp version. I dont know if it went bad or they wanted a larger one when the battery was relocated to the rear