Rsimos,
The ford trac-loc will work fine if you aren't going to race it hard or run slicks. I ran a Motorcraft trac-loc for a few years until I busted it and my stroker puts out over 500 pound torque. I figured with the light rear end I could get away with it and when I busted it the guy that built the Eaton unit up for me told me the down shifting I had done hurt it as much as the up shifts. But I don't drag race and am not dumping the clutch from a dead stop. When I had the Eaton unit done I also installed the 31 spline axels. The high performance big block Fords like my 1969 Daytona Torino Cobra came with the 31 spline setup from the factory. So the 28 spline would most likely be ok for you unless as stated above, you are going to really be banging gears and running slicks and drag racing.
Ron
