Milton Wisconsin here! The initial cost of a powertrax no-slip is going to be between $400-$500 depending on the rear end. The trac-lok is going to be about $225. Since you're having a hard time figuring out what axle you have, I'm going to assume you do not know how to set the backlash properly (which will ruin your day). This means that in order to install the cheaper trac-lok, you must pay somebody the labor. This will put you up to about the cost of the no-slip. However, the no-slip guarentees that you will not have one-wheel spin, even if one wheel is suspended off the ground! The trac-lok will not do this. The no-slip can be installed without taking the carrier out of the differential in a couple hours with no special tools needed. So, you can spend the money on cheaper parts & labor costs or just spend the money on better parts!
Summitracing.com
7.5" Powertrax no-slip P/N = PWT-92-0675-2805 (open case)
8.8" (28spline) Powertrax no-slip P/N = PWT-92-0688-2807 (open case)
8.8" (28spline) Powertrax no-slip P/N = PWT-92-0688-2827 (limited slip case)
8.8" (31spline) Powertrax no-slip P/N = PWT-92-0688-3108 (open case)
8.8" (31spline) Powertrax no-slip P/N = PWT-92-0688-3127 (limited slip case)
EDIT: Do not purchase the cheaper Powertrax lock-rite as these are sometimes known to have rougher street manners.