I have a 1970 F100 with the 390 and an Edlebrock carburator. It needs a tune up, but I cannot find a place to hook on my vacuum guage. No power brakes, so I can't use that vacuum line. In fact, this truck has NO vacuum lines beside the vacuum advance. It appears as though there is a port behind the carburator, but how I'd hook my guage up to it I do not know.