LS-K
Since your truck is the short bed, you need the 16 gallon tank, part number GM11C. I purchased the Spectra Premium tank listed above in your rockauto.com list. I got a better price on Amazon.com at the time I purchased mine.
Amazon.com: Spectra Premium GM11C Fuel Tank for...That tank can be mounted on either side of the truck. The sender is side specific for the '87 tank with fuel injection. I mounted ours on the driver side and used a spectra premium sending unit for an '87, part number FG05F.
Spectra Premium FG05F Sending Unit for General...
I used a Walbro 255 intank pump. The Aeromotive pump that Classic-Steele used might be a better choice depending on the power you are going for now or later...
The regulator depends on the LS engine fuel system. If it is a return style (2 lines at the engine) it has the regulator built into the rail. If its a single line system (returnless), then in need the Corvette Filter/regulator shown above.
Hope this helps.