The ComfyUI Mask Bounding Box Plugin provides functionalities for selecting a specific size mask from an image. Can be combined with ClipSEG to replace any aspect of an SDXL image with an SD1.5 output.
https://github.com/mikkel/comfyui-mask-boundingbox
git clone https://github.com/mikkel/comfyui-mask-boundingbox
comfy node install comfyui-mask-boundingbox