I've not done "real" research in PA that early, but I briefly checked the FHL Card Catalog, and it appears there are deeds back to the late 1600s. You should be able to order the microfilm for a small fee and use it at a local Family History Center, plus there are numerous published abstracts of early Bucks records, including deeds. Use the old FHL catalog and search by place at:http://www.familysearch.org/eng/Library/FHLC/frameset_fhlc.a...
In addition, the Pennsylvania State Archives has images of several of their early land warrant registers and surveys online. A good place to start if you find you're dealing with original grants rather than resale deeds is:http://www.phmc.state.pa.us/bah/dam/rg/rg17.htm#Surveys
Be sure to also click on the Land Records link/tab in the upper right hand corner for additional information.