filter landing is the width of the mating surface for the oil filter.
The remote filter in the kit you are looking at has 3/4" x 16 threads. They recommend using a Fram PH8A. This is a REAL common filter and many people make a similar filter (Fram, STP, Baldwin, etc) that you can cross reference too.
A lot of times these filters are on sale
at auto parts
stores, Walmart, etc for $3 - a huge savings over the cost of a Westerbek (or Volvo Penta
, Yamaha, Perkins
, etc) filter.
There are also numerous different lengths of filter housings with the 3/4 x 16 thread. This is all from memory, but they go from 2" to 8" long - so you should easily be able to find one that will fit in the space you have available.
Try and position the bottom of the remote filter so there is at least 2" of clearance between it and the bilge/hull/etc. You'll need this space so you can unspin and remove/drop the filter for replacing with a new filter cartridge.
It helps to buy the filter you are going to be using so you can get these clearances right when you are doing your installation!
A hot tip is to put a couple of plastic bags (one inside the other) under/around the old filter cartridge before you loosen/remove it. Once fully loosen, the used oil from the cartridge and the oil hoses will run into the bag - instead of the bilges.
Another hot tip is to fill the new oil filter cartridge with clean oil before screwing it back on. This will reduce the amount of time that you have a "dead spot" in your oil system.
Once you have installed the remote filter assembly, you can change out an oil filter in about 5-minutes and at a fraction of the cost.