Team321 (
www.team321.com) in Cocoa Beach, FL makes a double a-arm,
rocker arm IRS using an 8.8" diff. It can be supplied in custom widths for various
applications and there are a number of brake options available for it. There are
several photos on the site of an FFR chassis that was modified to take this IRS.
RCC Specialty
Products in Ft. Worth, TX makes a 9" based package IRS using Toronado half-shafts and hubs which they say is good for 650 hp. Your choice of
inboard or outboard brakes. Although the site doesn't mention available widths,
I assume they can supply it in various widths.
....Fred