Can I get a dtre engine into a dtr frame
Engine will drop straight in correct.
However it won't be as simple as that as you'll need the correct CDI.
The rest should be okay other than you won't be able to use the starter motor. There will not be the correct plug for that so that will cause issues.
You can't swap stator or genny over cause the crank is different.
So it will be a bit of effort getting it running.
But it will drop straight in