Todd, perhaps contact Kevin Zagar, owner/operator of CoolRyde Customs in San Diego, CA. Here is a link to his shop...
Kevin is a long time SOCer and is a cool dude. I know he has done many shortened IRS axles for customer projects. I'm sure he would be ale to provide the info you're seeking.
Best of luck in your endeavor. I look forward to following the progress of your build!
Thank you sir.....I will do so.