Looking at your previous posts, I assume you have a 76 280Z.
Using that assumption, I can make the following suggestions.
When making your own cold air induction, plan on the following:
Unit must be supported, some how. Do not plan on the connection to the AFM to be strong enough.
Do not used a material that has a smaller diameter than what you replace.
PCV has been used, as well as Mandrel bent aluminum tubing. Rubber toilet elbows have great potential (less than 10 dollars at any hardware store).
All connections should be air tight, and removable (don't construct something that welds or glues to your existing air passages! You may have to take it apart later).
Most people opt for the K&N. Figure out which one you need AFTER you construct the tubing. You may require the filter has a male flange that inserts into your tubing, or one that has a female connection that mates to your tubing. Size of the connection is the important thing. Don't get a filter with a smaller opening than your tubing, and then cobble it together. Find the right one. If the part store you visit doesn't have a wide enough selection, go elsewhere. This is the critical part, and must fit right.
Give some thought to heat shielding. A small deflector behind the filter/in front of the radiator will be beneficial. This will keep your filter from being damaged by the heat. Not essential, but something to think about.
Mount the filter as high as possible, but still in the airflow. This may help to keep some of the road grunge/rain spray off.
Many people have done this, look at some of the sites and see how others have done it. You may find what you are looking for, or find things you would do differently. If you just can't seem to make it work, you could always just buy one (for a pretty penny) from Motorsports Auto.