i have a couple of those old heaters, on mine, the line that comes out of the carb had a tee with a plug, i just took the plug out and hooked in a hose that came from my meter pump, when i started it i put a cup of diesel inside in the pot and lit with newspaper and started feeding oil,after it got going and warmed up it had no smoke just heat wave out of chimney,
the one i have has a cabinet around burn chamber, and has a fan that blows warm air out as well as provides combustion air
having a metering pump that you can adjust and maintain steady flow of oil is the key! using a needle valve to adjust oil flow does not work well as the oil viscosity changes with the temp of the room
does your heater have some sort of diffuser plate above the burning pot ? mine has one that makes flame swirl to burn better