1983 Datsun 710 excessive smoke from tail pipe

Have 83.5 king cab long bed, z24 engine, when engine is idling, it idles solid, but tail pipe starting smoking grey smoke with a hint of gas smell about 30 seconds after the engine starts, doesnt matter if engine is cold or warm.
When truck is going down road. No smoke, has plenty of power. The guy who had the truck, didnt know what he was doing at all, truck has been beat up. Wiring problems, the works, I need help here, ive been told the reason it smokes is from bad valve guides, rings, the the carb is choking itself, HELP ! LOL