An intercooler will definitely help keep EGT's a little lower, especially when towing. You don't necessarily have to have an air-to-air intercooler. If the packaging of the engine in the underhood area of your F3 doesn't allow for an intercooler around the radiator, you can always opt for an air-to-water intercooler and either run engine coolant through it, or a stand alone circulation system with a thin heat exchanger in front of the radiator. There are several guys on here and other sites that have run air-to-water with good success, so perhaps wait for them to chime in. If you're dead set on air-to-air, figure out your placement and dimensions and figure out if a stock diesel truck intercooler will work (for example, I used a '99 Powerstroke intercooler in my Fummins) or perhaps a smaller, custom routed "ricer" intercooler. It all comes down to packaging when dealing with a conversion, since nothing really came from the factory to fit that application.
Good luck with build, I'll be looking forward to seeing the finished product!