Thanks for the reply mateIn case you don't get a reply from the OP, you'll need to remove the electric fuel pump from the main tank and insert a length of fuel hose in its place. While you have the fuel pump cover off you can clean out the remaining petrol.
I used the fuel pump wiring to wire in a Carter lift pump that I fitted in place of the TB45E fuel filter in the chassis because you need to remove that too. That allowed me to keep the ECU function of running the lift pump for 5 secs when ignition is turned on so I get initial pressure while glow circuit is working.
Leave the sub tank as it is. It works the same for diesel fuel.
You'll need to cut out the fuel tank entry pipes to fit the diesel nozzles at the bowsers.
Otherwise, I kept my original 8mm fuel lines and simply connected them to the TD42 diesel filter.
I think most of my pics are still available in my conversion thread.
Ive already changed the filler over to a diesel filler as i managed to pick one up second hand pretty cheap and managed to snag a ZD30 main tank off facebook marketplace for $80 (full of diesel too ) so it already has all the bits inside i just need to wire the connector up.
Because my tb45 was gas i had to go down the route of removing the lpg tank and replacing it was a diesel tank
I had the same train of thought as yourself, keeping the ecu function running the pump to pressurise the lines helping my 10mm pump (This will be replaced at a later date when the funds allow)
Im a right in saying that i only need 2 fuel lines coming from the tanks to the injector pump as the return lines are no longer needed ( bleeder rail returns fuel back into pump ??)
im going to check your post out after i post this may even steal some pictures for reference haha