I'm guessing this is the gem you got on ebay??? I saw the car in person, pretty solid ride. I've got a 66 912 as well...fun car. I'm rebuilding the engine this winter, you're welcome to hangout, etc.
I'd stick with the 4-speed if it's in good condition, otherwise you'll be running through gears too much, especially considering traffic in our area...I'd gladly trade my 5 for a 4 on a daily driver.
You may also want to look into getting a later engine, I'm tempted to find a nice 3.0 or 3.2 for mine...

, but will stick to rebuilding for now...
Congrats, from what I saw you've got an amazing deal on the car....