The 87-89 tanks are all around 1/2" shorter than the 86 tank but all three will fit the 86 frame. I fitted an 89 tank to my wife's 86 & the front mount wouldn't line up to the bolt hole without removing the aluminum crush collar. I ended up making a 3/16" spacer out of kydex plastic to move the mount forward & that took care of the alignment issues... Another option is to polish your 86 tank. Assuming your's is red those are pretty easy to restore, even if the sun has faded the tops white. I polished a red 86 & a red 87 tank & they both had faded white tops & both came out looking like new. The blue tanks on the other hand are a different story, if they have that green tinge I've learned it's next to impossible to get them back to the original blue color.
