I would like to add something about the HP increase, it is not so much in increase as a prevention of loss.
The engine does not make more power with the CAB, but it prevents the loss of HP as the under hood air heats up and becomes less dense.
If you have driven an LBC on a really hot day and idled in traffic a while you may have felt the effect, which is a noticable decrease in power.
As far as the filter, they make similar conversions for cold air feeds for modern cars, lots of filters from K & N etc. available mail order or from the auto parts chain stores.