Doing a solid rear end will not be cost effective if done right. The amount of time and fab work it would take to do this would be insane and to the point you might as well back half the car. Now I would love to do this and there is a reason why peole are getting rid of there IRS for drag cause it just works. But it wouldn't be worth it for the everyday person. The hardest part would be getting the geometry correct and taking the time to fab stuff and ripping everything out to the point where it might as well be fully tubular rear end with a 4 link