wrong wrong wrong. Do the 3.8L Ford Taurus e-fan, then get a fox body (i think) stang reservoir. That res has a round side to snug up against the fan shroud, and hold about twice as much coolant as any S chassis part.

*edit* here is a link to the mustang reservoir in question

Or you could just hit copher's every week for a year. I have 2 perfect ones!