A few days ago I found a 77 Penton 400 in the recycler for $150. He said it was clean and in good condition, only needed a pipe.
Checked it out, without telling the wife.
I saw it and it was in complete condition minus the pipe. I could't help my self offered $130 and he took it. Going to take it to my brothers house.
Wish me luck. Dan.
Check on e-bay under KTM and I think there is a pipe for sale that will fit your 400.
Good find on your bike and good luck with it.
Rocket