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1958/75 P500's offered two wheelbases: 137" & 154."

AFAIK, the Condor's were built on the 154" wheelbase.

What 4WD anything has a w/b that long that would work?

Marmon-Herrington converted some F600's to 4WD with a w/b of 156."

Some F350 4WD's have a 155" w/b, but once behind the rear wheels, the frame is too short to accomodate the length of the Condor's body.
Condor's were made from the early 1960's thru 1975, the last year of the P Series.

I've seen at least two with Y blocks, an engine used prior to 1965.

Type Condor into the search box, a whole bunch of refs come up.