those bikes are all over craigslist for $100-150.
in my opinion, those bikes have been done to death (and i think they're pretty ugly.
) putting the ktm clone on one would make a fast, clumsy looking bike with poor handling (again, my opinion...)
you say you've got fabrication skills, so if you can weld, why not go all out and build your own frame? if that's too much for you, chop up a couple bikes you like and create something totally unique.
this forum is filled with custom bikes so you should find plenty of good examples to spark your creativity.