The carb to air cleaner flanges have two fixing holes centrally across the intake and two smaller holes above that and closer together. These smaller holes allow the underside of the piston flange to be at atmospheric pressure while above the flange is subject to inlet manifold vacuum controlled by the butterfly. If these holes do not have a free passage to the outside world via the air cleaner gasket, cleaner base and air filter, the carb piston cannot rise as it should and the result is a rich mixture:

Originally the gasket was 'handed' in that it must be the right way up as here so that as well as the bolt holes lining up the breather holes in the flanges are clear as well. For the 4-cylinder the gaskets are the same for both HS and HIF:

But on a friends 78 I found these gaskets which can be fitted either way up - brilliantly simple. But then you can go and spoil it all by installing the air-cleaner base-plate the wrong way up!

The HIF flanges on the V8 are quite different. Looking like a Swiss cheese on the left, but with a gasket fitted (right) there are just fixing holes and piston breather holes remaining, as with the 4-cylinder:

The gaskets and blocks for the inlet manifold side are also handed, no holes to line up in that case, but logic and nicety dictates that they should be orientated to match up with the outline of flanges on the carbs:

Looking at the inlet manifold from the carb side they should be fitted as shown here:

And yes it is the same as looking at the carb flanges as they fitted as a mirror image to each other.