You can install a IRS catback in a SRA equipped car no problem. Its actually a relatively common thing for ppl who have really aggressive suspension setups.
As whether to tell... just look under your car. If you have an IRS you'll have control arms, if you have a SRA you will have a big solid tube. It is literally a 5 second "oh I have X" check.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.