[Jubbie]

On my 77 euro engine the vacuum tap for the dizzy was in on the engine fan side of the trottle body. The port pointed out towards the drivers side of the car. I would guess it is in the 1/8" to 1/16" OD range. There is also a vacuum tap on the firewall side of the throttle body for the decel valve. If you use it, I think the one on the engine fan side of the trottle body since it taps in just under the butterfly and looses vacuum when you get off of idle.

If you have any pictures, that may help.