Looking at the A/FD for Clark (actual name of the airport at Williams), and it's not showing any info on weight bearing capacity. The runway is 5,992' x 100' with 2-light PAPI's at both ends. On airnav.com, it mentions that Rwy 36 has a 479' foot hill 8,800' from the end of the runway on the centerline, and Rwy 18 has one 393' high 7,800' from the end of the runway. AvBug's right though, there are numerous other obstructions in the area, namely Bill Williams Mtn. which is about 3,000' AGL and only about 5 miles south of the field.
As a sidenote, the airport museum that AvBug mentioned is actually at a little wide spot in the road called Valle (pronounced "valley") identifier: 40G.
Hope this helps.