well i got to see the pictures
first off that data plate is german? never seen a yale forklift with a data plate like that, are there any other plates on the machine? on the dash? on the kick panel behind your feet? on the hood? or on the front of the firewall between the mast and truck frame?
secondly the picture of the rear of the truck doesn't tell me much but does give me a general idea of what year it was built.
what would help is if you took a picture of the engine
also on the engine block near the rear of the engine at the seam where the head meets the block there should be a machined area that will be stamped with FE or FA or F2 or something like that. You may have to clean that area to see it. If you see markings like that then this is a mazda engine. That's what these trucks generally came with. They also made a D5 engine and a diesel engine, the D5 has a timing chain and the valve cover is shaped differently.
Take a snapshot and i'll tell you what's in it.

The truck serial number should be stamped in the frame of the truck on the RH side somewhere near or behind the hydraulic tank cover, if you open the door and clean that area you'll find it stamped somewhere there. OR in some cases it might be stamped in the front fender or firewall area up front near where the frame meets the drive differential area.
In either place it should be in plain sight.
Note: if the truck has ever been sanded and painted it may be painted over so it may be hard to see at first.
All i need is a serial number of the truck and that stamped engine model code and i can probably get you the part numbers of the gasket.