I'll check later this morning, but I'm pretty sure that the intake boot from a YZ125C goes onto the late DT175 barrel. This will allow a 30~34mm carb (at least), although I haven't worked out a decent solution to join the larger carb to the airbox.
IIRC: Twin shock and early monoshock DT175s have a 26mm carb, while the later monoshock bikes have an oval-bore 24/27 (or similar).
Looking at older IT175s and YZ125s will give you all of the 'fun' stuff you could dream of (in a vintage context, at least).
I have a late model pipe that you can cut up, if you don't want to touch yours.
I'm currently considering fitting a late DT175 engine into an IT175F frame for the wife - still road legal, less weight and better suspension than the DT.