28 Spline or 31 Spline (8.8)

[00t444e]

Aren’t those for off-roaders? My build is a street truck.

No they are for street and offroad use, they work great on street vehicles, I have been running them for years.

 

[4x4junkie]

A locker is overkill for a street truck... Off-roaders put up with it's handling quirks on the street as a tradeoff for the superior traction while off road. You could use a manually-selectable locker such as the ARB Air Locker (avoiding those quirks), but your selection is then between a spool, or having an open differential. Unless you're drag racing, the limited slip seems like the better (and of course cheaper) choice IMO.
There is a selectable locker that is a limited slip when not locked (ECTED, I think?), but history has shown it to not be very reliable. The Detroit TrueTrac is a solid choice though.