Correct...the '87-up E7TE heads were in fact F150 heads of the same year. The '86 heads might be a lot more restrictive if they're also the same ones from the Mustang of that same year, so I wouldn't chance it.
Also, keep in mind that the 351W heads will have 1/2 head bolts, so you'll either need to sleve the head for the smaller 7/16 bolts, or drill and tap the block for the larger ones.
Either way...the 351W heads of the 80's held no advantage over the 302W heads. Valve size is the same, as are the intake and exhaust ports.
If you want to work them over, that's fine...but for what it might cost, you'll probably be further ahead just buying a used set of aftermarket aluminum heads and calling it a day.