Interesting collection of bits! Do you think the tank modified for those forks? How was clearance between the forks & tank at full turn?This bike was put together from parts and the fork is from a Horex and the frontwheel is a Münch Mammut one.Unluckily the hub is cracked and is made from magnesium which can not be weldet I think.The UFM is the early type with no slot for the rear damper.
Unfortunate that the wheel is cracked. Magnesium can be welded successfully. I watched my father gas weld magnesium chainsaw bodies in the '70s. It is much more controllable with modern TIG welders.
That said, I would be reluctant to weld it. Machining the resultant distortion out of it can be difficult. I had an aluminium Grimeca hub welded once. I did machine it adequately to go back into service safely, but it wasnt really worth the effort. Magnesium distorts worse than aluminium, even without welding it. I have machined some shocking Mg aircraft castings, they just keep going back into service for another lap!