Looking through the various threads here, Armandos, and in the Originality and History Forum, I can't seem tofind a definitive answer to a question regarding heating.

It seems as though the early /6's didn't have a fan to push air into the cabin, and relied on the engine fan for this, while the later /6's had fans similar to the /4's.

Can anyone clarify this, and, as an additional question, is the air pushed by the engine fan sufficient for heating, or should one install the block-off plates and proceed with the electric fan option?

First I've heard of this. Can you post a reference that leads you to believe this?
I have never had too little air in a 914/6. I've had too little heat in the air on frosty mornings, but this is a factor in any air-cooled car - no load, no heat.

I can't imagine needing more air.

No real six ever had a fan other than the engine cooling fan and the defrost fan.
With good heat exchangers, (good luck ! ) good control valves and hoses and properly adjusted pulls, heat should be very good.
If the engine leaks oil, you'll smell like a french fry.

I don't know of any change to the later sixes. As folks have said, the
only air going into the heat exchangers (and then out) comes from the
engine fan. Haven't had mine hooked up in a while, but I remember
redlining it in 1st and the defrost vent blowing my hair around.

The early cars (6 and 4) did not have a vent on the front of the dash,
just windshield and feet.

Ain't that the truth!!! Some times I think it is the fumes that cause my kids to sleep in the car rather than the loud hum of the engine.

Put it this way. The 2.4 in my bus made enough heat driving down the freeway that you had to crack the windows a bit, even on the coldest of days.

The Cap'n

Cabin blower fan .... never noticed. I use the defrost fan when necessary and as far as cabin heat, when I use it, there's plenty there, though it takes a little longer to warm up than the Benz.

Though my current six is not running......my last two did not have a blower for the heater that I recall and I just used the lever to adjust how much heat I wanted and it always delivered. I was never cold in that car when it was cold out.