With that few of miles, I would suspect the valve guide seals to be the problem. Due to sitting so long, they have shrunk and perhaps aren't making a good seal.
Before making the jump to replace them, may want to run a quart if Marvel Mystery Oil in the crankcase. I've seen it do wonders, but the vote is its Snake oil. I usually run 1/2 quart in all 3 Ford vehicles I drive, when they get 1/2 quart low, which is relatively close to 3k miles, then I do an oil change. I don't use synthetic as it burns/drinks faster in older engines, which have looser clearances. Perfect for tight tolerance, new engines though.
Is the PCV valve routed to the rear of the intake or center on a 460? On the 302, 351, before '94, they were and lead to #8 piston grenading due to the routing of the PCV valve, since all the trash would get sucked into the last runner, and then into #8. Ford designed a new tube to route the emissions to for the PCV valve to the center on the plenum.
Is the PCV valve you have correct for the 460? Is it a cheap Fram, Autozone, etc version, cause a Motorcraft PCV valve is the only correct one to use. Those made by companies mass producing in 3rd-world countries are crap and only copied Motorcrafts' design. If you haven't changed the PCV valve, then spend $12 and get the right one from the dealer or local parts store. Likely, you'll have to wait a day, but you can scratch that as being your problem. Cheap copies can actually allow to much vacuum to pull from the crankcase and when you are slinging the RPM, just act like a vacuum sucking oil right into your intake and burning away.
1992 F-150 I6 4.9L 300 110K 4x4, SuperCab, Manual
1992 F-150 V8 302 156K 4x4, SuperCab, Auto
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