in 1986 did they put the same rear end gears in the chevy truck?

Call an auto salvage yard and ask them. They have a set of books that shows what rear ends were installed OEM and what rear ends are interchangeable.

what ? do you mean if you got a rear end out of another truck of the same year would it work then yes. as long as it's the same transmission type ( auto or standard ) and the same ton-age it should work. it's better to swap out the whole rear end than trying to change out the gears.

yes