I finally got around to update my attempts to adapt pleated paper air filters to replace the standard K&N oiled cotton gauze filters.
I sourced a couple of filters from the FLAPS (AC-Delco A178CW, about $4-5 ea.). As in previous attempts shown, these pleated paper filters are a very tight fit into either housing. However, the K&N al. cast bases/tops are slightly larger by a few mm than the lighter stamped al. housings by Filtron). However, these filters are replaceable and cheap. Many independent tests show pleated paper filters do a better job than the supposedly superior K&N oiled versions.
Comparison
The AC filter is this much taller than the K&N:
Installation
Instead of removing the outside metal grill (see Mark's post, #28), I opted to remove the inner screen to reduce resistance to modify the ID to fit better. Careful. Wire ends are sharp. Use pliers or equivalent.
Pull random wire strands from the rubber surround. This reduces the number of puncture holes in your hand as well as avoiding loose wire ends sucked into the intake.
Per Mark's option B, I removed two sections of outer grill to again reduce any resistance to reshape the filter.
It's still a tight fit in the Filtron housings. There's still a tendency for the sides to bow slightly inward (exaggerated in post #23). I bent some scrap material in a U-shape to keep the inside walls parallel.
Completed install in my 914-6 conversion:
Sherwood