I have done some thought and converted a few cars to WVO.
My first was a Mazda '90 Capella 2.0 litre NA diesel which had an engine bay 17litre tank. I tried both looped and return to tank of origin. When that motor died due to loss of coolant, the supercharged replacement took some of the place where that tank sat, so a fiberglass tak was built in the load area. A HiH fuel heater was used and the tank had a 1 meter * 12mm heat exchanger built in.
I now have an '84 300D and it's conversion is configured with a looped return and an electric lift pump at the WVO tank in the boot (oops
trunk).
I have documented some thoughts on conversion topologies in a ddocument on a friend's website at
http://www.shortcircuit.com.au/warfa/Veg-oilOptions.pdf.
Please feel free to ask for clarification as required.