I don't have any direct experience with going from FI to Carb but I have a carby car. You could install an external low-pressure electric pump near the tank and get a fuel pressure regulator and set it up for 3 psi. Another option is to use the DX camshaft which would allow you to use the stock DX mechanical fuel pump. The DX camshaft is longer and has an extra lobe that runs the mechanical fuel pump. You'd have to find a DX camshaft though.
Hopefully someone with some experience doing this will chime in.