From what I understand, unless you are pushing the L5p to the point of maxing out the transmission capabilities (which would be the wall you will hit first in your quest for L5p horsepower) there is no need for any outside lift pump. The new pump inside the tank on the l5p is plenty and thus far has not proven uncapable of handling a substantial amount of power. By the way- you're not even deleting your truck so why do you think you need one? Your factory fuel system in your l5p is MORE than enough for the basically stock power you will be producing even with the derringer, sorry.
Oh, the reason you can't find a video on a install is because people prefer not to throw money away. Unless you are doing a compound turbo on a L5p (which would be sweet) you don't need one.
2018 GMC 2500 CCSB - Denali - White - L5p