Thats not really all there is to it, but when you have 
both tanks on the ground next to each other, what needs to be
done is rather obvious.  And yes, you do need to have the vent
from the center of the '68 tank connected to the inlet that you
removed from the '67 or else you won't be able to fill the '68
tank completely.  Your friendly neighborhood vw dealer has the 
rubber "thingie" that will connect the '67 inlet pipe to the 
'68 tank.  I used a piece of steel vacuum advance line that I
had a friend braze into the '67 inlet pipe.  Email me if I can
help.
					Forrest Minor