This is how I did my conversion. I have a 21 gallon boat fuel tank made from alluminum. I took a 300 td oil cooler, cut a hole in the tank and installed in the bottom of the tank and welded a couple of nipples for the heater hoses.Then welded he tank back. I think this makes a real robust heater. That is my in tank heat exchanger. I also installed a 500 watt mb block heater in the bottom of the tank.(plugged in overnight it took my oil to 120 c) I took a fuel cooler from a 126 body car (the one that is in the suction line and installed nipples on each end and I have one aprox. under the rear seat area and another by the steering gear box. These make wonderful in line heat exchangers.The coolant from the engine passes through these heat exchangers first so the fuel will get all of the coolant heat closer to the engine.I used a pollack 6 way switch over valve ,plumed it as close to the injection pump as possible. for my filters I scavenged the factory filter housing from another car like mine plugged the "injector return line" return banjo . and installed a clear prefilter also. I have a 4psi electric pump inline also. I took a coolant temp sensor from a like car and installed it in my aux tank along with a fuel sending unit. now I can flip a switch and get my level and tank temp using my factory gauges. It is really working well. The 126 body fuel coolers turned heat exchangers works very very well.I have about 800 miles now without the first problem

Sounds like you have a working system. I would only suggest to replace the pollack valve -or carry a spare. Pollack valves are infamous for failure (at the worst times).

The pollacks are fine for their engineered purpose-moving petro/diesel from port "A" to Port "B". On hot veggie not so much.

Cracks, leaks, stuck positions, failed motors, fried inarads and stuck plungers are more common then not.

A similiar valve from Greasecar or Hydraforce is made for the near boiling oil temps and worth the small fee.

The tought of hitting a pollak valve with oil at 120c makes me nervous. Got any pics of your system?