Boeing Boy, what is the exact designation of your PA-28? Have a look at the TCDS as applicable to your model. (TCDS 2A13),
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/58e3800616d183568625805f00534b82/$FILE/2A13_Rev_56.pdf
it will tell you the maximum prop diameter. I'm seeing diameters from 72.5" to 82" depending upon the model of PA-28. From experience with EASA and noise compliance, I suggest that you will be too burdened to install a prop which exceeds the TCDS diameter for that model.
PM me if you need more detail.