AURORA, Colo.--While it may take two years to field, a dual-mount bulkhead in the nose of the Lockheed Martin [LMT] F-35 to accommodate both the AN/APG-81 radar or the twice as powerful AN/APG-85, both by Northrop Grumman [NOC], may help in the F-35 program's move to Block 4, of which the APG-85 is a critical part. The dual mount is "an opportunity on a number of fronts," acting Air Force acquisition chief William "Elvis" Bailey said on Wednesday in a…