P: Toggle Crop Guide Overlay without being in Crop Tool

It would be nice if LR had a crop guide overlay that can be toggled on or off without using the actual Crop tool. For instance, my camera shoots in 3:2 aspect but I would like for there to be a 4x5 / 8x10 cropping overlay that can be constantly on (or toggled off) so that I can edit for common crops that my clients might purchase such as for an 8x10. 

If there's already a way to do this, please advise, but otherwise, it would be a VERY helpful feature. Thanks in advance!