When travelling down a light grade (3-4%) this morning, my 74 2.0L let out quite a bit of smoke. Basically, I was in 3rd gear, roughly 3,000 RPM, foot OFF the gas, clutch pedal NOT depressed.

Where is this likely coming from? Something dripping on the heat exchangers?

You need someone to drive behind you and have them determine if the smoke is coming from the tail pipe. What you describe(smoke on decel) indicates worn valve guides.

Exactly the problem I had on the way to RRC. Leaking valve guide dripping onto headers. Only happened going down hill until it started happening all the time.

I thought that a leaking valve (exhaust) guide meant that exhaust is exiting through the valve cover (crankcase).
A leaking intake valve guide would leak oil into the intake valve. (which would be worse under engine braking)

How could a leaking valve guide leak onto a header?

Do you mean a leaking pushrod tube?

I wished mine had been a push rod tube. I was really hoping for a leaking valve cover gasket but, alas, it wasn't either of those. Besides I seal my push rod tubes with hi temp silly cone. They never leak.

The engine will suck oil through the exhaust guides when off throttle. Get some one in back of you to check to see if it is coming from the exhaust. If that is the case you can put it is neutral until you choose to make the repair.

BRuce

Ah.. yes, so when Elliot said

He meant INTO headers...... that makes sense