Jon, this is what's listed on the .net site (you know, the site that actually has usefull information):
"The Mach 1 came with the larger engine, the 2.8L V-6, and a unique lower bodyside treatment with Mach 1 lettering. However, the Rallye package was required to give the Mach 1 the maximum performance potential. The package consisted of the Traction-Lok differential, CR70x13 wide oval radial B/WL tires, extra cooling package, digital quartz clock, the Competition
Suspension(heavy-duty front and rear springs, rear stabilizer bar and adjustable shocks), outside color-keyed remote control mirrors, leather-wrapped steering wheel and styled steel wheels/trim rings."