I did the suggested air box mod on my 95 PS F-450 dump truck and 97 PS F-250 pickup and used the NAPA 6637 filter (actually the Wix 46637 wich my local parts store stocks @ $35 each) You can clamp the stock rubber boot right to the filter collar but the boot on 95 & 97 PS's isn't long enough to allow filter to reach space between battery box and brake master cylinder. Apparently the boot is longer on latter PS's from the photos I've seen posted.

So, I cut 4 inches of the plastic tube off of the top of the stock airbox with a band saw. Just cut straight thru the whole top of the stock air box at the 4 inch mark you make on the tube. Then trim off the part of the air box top that is still attatched to the tube and dress up the cuts on a belt sander.

Attatch stock end of freed up tube to the stock rubber boot using stock clamp. Insert newly cut end into filter housing end and clamp with 4 inch band clamp. Total cost: $35 + price of 4 inch clamp.

The filter now wedges in the space between the battery and fuse box and allows full circulation around filter. I reinstalled the stock air inlet that goes overtop of the battery as it should help blow outside air directly on filter.

As a bonus I can now hear my turbos sing.