You can bolt a DCOE carb to this adapter but the DCOE is a sidedraft and the IDF is a downdraft so unless you have a custom application the carb will not work correctly. I've sold several of these to people mounting TB's to IDF flanges and they've had no problems.
Please take note of the direction the carb is facing to make sure it will work for you. I can make them so the DCOE will mount the other way, just ask.
These have 40mm throats but I can make other sizes so if you need a different size, just ask.
I do combine shipping so if you buy multiple items, let me send you a combined total.