Sorry, I then mixed it up. For sure the '91 has the OM364.
Well, some people say, it's the best engine available in a Landcruiser
The OM364 is the 4-Zylinder version of the very famous OM366. At least in Germany and in South Americas it's a very common engine. There are many applications, in some of the Unimogs as well.
For the Mercedes-Engines, there are many versions for the oil and fuel filter available. I have the OM314 (precessor of the OM364) and use the filters of the OM364, because it'S a '89 version of the engine and in between the model changes they kind of mixed the parts.
From here in Brazil it's hard to search on USA-sites, but look for the OM364, OM366 or the last build OM314/352 engine oil filter. For example a MANN HU932/4x should fit.
There are 2 versions of filter, a long and a short one. I guess (pretty sure), that you have the short filter installed.
-> H932/4
-> OX150D
-> A0001808009
Again, if you don't find the fuel filter as spares, you can replace them by some cartridge system or so, those are very common in different sizes avail.