I thought the SRA swap dropped closer to 150lbs not 75?
Besides the weight drop it changes the way the weight is distributed on the rear. Arguments can be made for keeping the irs as it is sprung weight but it comes down to usage.
Weight can be pulled out of the irs but it’a minimal and is mostly just control arm weight which is maybe 15-20lbs. But they are infinitely harder to go fast in the 1/4 with the irs cars barely breaking into the 8’s after all these years.