I find it funny that when the debate of SRA vs IRS comes up nobody ever mentions a word about those two components adding weight. I think most forget that adding a quality set of LCA's like a set from MM will actually add a few lbs. When I started kicking the idea around of swapping in an IRS everyone I talked to was real quick to point out the weight issue. After doing the swap finally I look back and wonder why I didnt do it years ago.
When I measured the weight of my IRS and the weight of my old 8.8, it was approximately 100lbs heavier. I did this with a bathroom scale, but it seems like an accurate approximation. The biggest thing is even though it adds weight, there's less of it flopping around on the pavement. I don't regret my IRS swap for a second. I'll be removing it from my fox and swapping an 8.8 back in just so I can sell it (the car). The IRS is getting a bushing upgrade then being dropped in my new 94 GT shell
IMO, I'd buy a set of SA konis for the whole car. That way, you can fine tune if you need to. There are times I wish I could get my car to ride a tad bit softer on the street. A friend has SA konis on his Taurus, and it's amazing how he can go to an autocross, turn them up a few notches, run the day, then turn them back down to cruise home in comfort.
FWIW, I haven't had a bit of problem out of the strength of the IRS. It'll wheelhop on certain surfaces (tires affect it a lot too) but if you're already rolling, you're golden. Granted, I'm on stock 93 302 power, but as long as you aren't doing drag strip launches every friday/saturday night, you'll be fine.
Also, I suggest getting a larger front swaybar for your car if you install the IRS. My car was stupidly prone to snap oversteer without it. I installed an eibach front bar after I spun the car on the dragon and at an autox (that was messy). The car became immensely more balanced with a bigger front bar. Higher springrates in the front would do the same thing if you don't feel like swapping bars, but you didn't mention anything about that, so I'm assuming you've got a stock front end.