After countless trips to various hose and tubing specialists, and getting a different opinion from each one, I finally decided to go with the CAT recommendation (picture attached). Both CAT Parts and Maintenance agreed that this was the correct line to use. I really considered the plastic tubing route, but I couldn’t really find anyone to help, including the ParkerStore, that makes the stuff. They looked at me like I was from mars and had never seen the stuff I had printed out for them. And, I couldn’t blindly order parts on line, not knowing exactly what I would need. So, CAT was beyond helpful and it’s their engine, so they ought to know, right? It’s another hydraulic line that is supposed to be diesel stable, and it was cost effective, about 30 cents an inch (much better than the $15/ft Teflon stuff one company recommended. Adds up when you need 45 feet!) I also had them make the line from the primary to the transfer pump from the same stuff. Incidentally, they said this was the same line used from the transfer pump to secondary filter, when the engine was manufactured. I can run the new suction line in a way that it can be removed without too much difficulty, if it ever needs to be replaced. Hopefully that happens long after I’m gone! Thanks for all the help on this.