spools dont act to good on the street...
just as todd says, they try to go straight when you turn, they wear tires quick, and can be hard on axles. spools can be used on the street, i have one in my shortbed chevy, its heavy and i have to work to turn it. for straight line racing they work great.
a locker, cog type units are also awkward on the street, i had one years ago in another chevy truck i had, the clunking when it locked and unlocked was annoying as heck.. for straight line racing they work great until something breaks, i broke 2 in my old truck years ago.
i had a 8.8 in my 84 mustang, its a clutch type limited slip, i rebuilt it and added an extra clutch in it effectively tighening it up, and it worked real well.
i also had a limited slip in prior to my 9inch in my current shortbed truck that is narrowed, and something was wrong with it, and it was dangerous to drive, if the tires broke loose it would point you to the ditch, and it pushed left and right if you did a burnout, it probably needed work but i dont know, had a guy tell me it was more than likely a 60/40 limited slip, and when it broke loose it was engaging and disengaging which was pointing me in different directions..
I myself on the street like the eaton units, and the auburn units. ive had good luck with both..
adding this... i'm with donsrods ...with my roadster, i have 2 rearends for my roadster, ones the frankland quickchange with a spool, the other is a 9inch with a 3.70 gear out of an old style bronco, more than likely a locker unit, and i'm kind of apprehensive to use either, i would just assume to use a single trac in a T, it would be more driver friendly.