You are correct to a point, Richard, excepting that I believe quite a few '87 turbo Buicks went out the door as late as late '87 with the earlier power steering reservoir. I do not remember on mine whether the cap rotated in a different direction, but I can tell you that the reservoir was different itself. The old one had pretty small lines going to and from. Either the inlet or outlet boss / nipple was located differently, and contained a right angle pointing downwards, I believe, and the reservoir was smaller. The new design / replacement was bigger, different molding, larger outlet hose nipple, 1 hose located a little different, & there was something inside the reservoir that rattled when new, part of the design, I guess.