My lift went inop also, after much research and debate I found that the new diesel fuel additives are mostly ethanol based and have a very high acidic base. This causes the gaskets and the pump impeller metal plate to erode and fail.
After a lot of reading and consulting with Cummins Diesel mechanics, I found out the latest lift pump for my ISC 350 (made under contract with Cummins in China) has a neoprene based gasket and a corrosion resistant impeller plate in it. Priced it around the US from Cummins dealers, best price was Cummins of Tuson (can't spell) AZ. With shipping under 400 bucks, around Jan 2021.
Not a easy first time install, you have to go in from the top and work around the turbo, requires someone (my son) with LONG Arms. Got the Cummins parts warranty, the only thing that caused mine to fail was the new blended fuel ⛽️ Runs perfect now, took about four hours since it was our first replacement. Two hour job for a skilled long arm tech that's familiar with the system
I went back with stock reasoning that the first lift pump lasted 22 years (2000 Dynasty) and at my age ( classified-lol) the replacement stock pump would work and save a few bucks and last longer than me probably