Sometimes when I drive my car, I get a rotten smell that makes your eye's shoot full of tears, but that's usually when I had a bowl of beans the previous night...
No seriously, you say you've rebuilt the engine, and it's only run 1500km, it might be that there is still a lot of oil left inside the exhaust system from when the engine was in a bad state. It's gone and gathered in the cans and pipes, so it will probably take some time for all of that to burn away. Taking it on a long trip, and giving it a couple of long extended runs at full throttle might heat the zorst up enough to get it burned clean quicker.
When you park the car, the fumes aren't being blown out of the zorst, and that oil get time to cook in the hot system, so it will expel lots of pungent oil fumes when parked in the garage. That will explain the "old-oil-in-clothes" smell...