even upgrading your IRS there is still a chance that it could break. when they break its expensive. you could build a nice SRA for with all the good stuff and sell your IRS and come out with money in your pocket.
if the IRS was so great then why does ford not use them in the shelby, steeda, roush, saleen, or even a mustang gt.
IRS are good by design however fords IRS is weak and not fully developed well like they have in the vetts and vipers.
my advise is to build an irs with good suspension and have lots of fun.
Yes, the IRS is a more complex suspension and is more prone to breaking then a stick axle but that happens almost exclusively from wheel hop, massive clutch dumps and hard launches. I laugh when someone can’t understand why the OEM driveline breaks under those circumstances. In case you haven’t noticed Ford is the lone holdout for having a straight axle in their performance cars as both GM and Chrysler employ an IRS. Ford stuck with the SRA in the S197 due to cost and weigh reasons only. It more likely than not the next generation of performance Mustangs will drop the SRA as well for better road manners.