Mike, my
oil filler tube on the front of the intake sticks out 4 1/8", so that's probably the standard length. I don't know of any others available. I have chrome pentroof valve covers, and my breather just touches it, so I can see where you'd have a problem with the thicker aluminum covers. I believe the breather on my front tube is larger in diameter than the originals, so I'm going to guess that's the direction you need to go...a smaller OD breather. Sorry, don't ask me where. With so many people running the aluminum covers, there's got to be one available.
I suggest you run the PCV out of a valve cover and block off the rear breather hole in the intake. As you've been told, all you need is one fresh air intake (breather) and one PCV. You can run the PCV to the large tube on the base of the carb. It should be the same size as the tube coming out of the PCV valve (3/8").
Dan