Will 1990 Toyota 4x4 pickup bed fit 1986 pickup?

No, the bed of a 1990 Toyota 4x4 pickup will not fit a 1986 Toyota pickup. The dimensions of the beds are different. The 1990 pickup bed is approximately 6 feet long, while the 1986 pickup bed is approximately 5.5 feet long. Additionally, the mounting points for the bed are different between the two models.