The lift pumps work best back at the tank pushing the fuel rather than pulling it.

You can loose a large amount of heat in a relatively short amount of uninsulated fuel line. Your 12v heater should be as close to the injection pump as you can get it with nothing more than a small inline filter between it and the pump.

Some people have reported clogging there FPHE the polymerized oil and having to clean them out. The more animal fat you run the more problem you would have with this. I use the arctic fox stainless heat exchangers. You won't get as much heat gain from them but they don't build up with polymerized oil.

Is your fuel return looped back to the supply or does it still return to the tank? Looping your fuel will increase your fuel temps and put less strain on your lift pump. It will also trap any air in the fuel system in that loop so you'll want to make sure you have no air leaks.

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1982 240D 617turbo 4-speed 225k miles ,boost and pyro gauges, home made two tank SVO setup
1982 240D "Cream Puff"auto 313k miles two tank SVO setup
1996 F-250 Powerstroke 186k miles, bone stock (possible donor for the 1970 F-350)
1970 F-350 "Bertha" 460, 4-spd, 72k miles, 12 foot flatbed, needs a diesel!