I don't believe so. Most of the lowering springs out there for the 03/04 cobras are designed specifically for the IRS. $75 is a great price for H&R's but I wouldn't chance it.
I remember when I bought my H&R Super Sports for my 03 the description was for 99-04 v6/GT/Mach 1's, no cobras because of IRS.
12 Black GT500 SVT PP l 2.6 Pulley/Idler l Airaid l o/r X l 305 NT555R's l Recaros l
04 Azure Blue Mach 1 / 03 Sonic Blue 3.8 / 14 Sterling Grey F150 FX4 402A 5.0 / 11 GT500 R.I.P.