I have a twinshock DT175 bike , a few years ago I had a mono shock DT175 engine and looked at doing what you suggest
as far as I can remember the mountings were not even close to lining up and I abandoned the idea.
{ I don't think there are even many interchangeable parts between engines }
However as has been suggested , if you can cut & weld then anything is possible.
To clarify - the bike I have is a DT175C , but I didn't know the exact model year of the monoshock type DT175 engine I looked at fitting
the DT175A,B,C engine cases do look visually the same as TY175/125 and YZ125C,X , but I think the YZ & TY are all 6 speed {could be wrong} whereas the DT175ABC are 5 speed , so I don't know if cases are different internally to suit the extra gear ?
over the years I have had all the different engines , but never really got round to seeing what was interchangeable apart from clutches , which I found there was quite a few different ones .