I would stay with the 3936316 it has not superceded.
The 3936317 is indeed a lift pump, but I'm not sure of the difference.
My source at Cummins tells me as I type that he is unable to "back" into a ESN or CPL with the 6317 number.
If the price is right and you don't mind the what if. . then go for it.
It is not my favorite thing to change, but thats my humble . 02 opinion.
OBTW the two gaskets for the pump are 3939258
Good luck