although the parts
are interchangable, I will say that
without a doubt (as i had an issue)
the 86 and 88 bikes bottom pan had some slight casting differences in the area / recess the filter occupies. I found this out when I got one of the original SPOOFAK's from Dan, prior to his re-design of the adapter. The oil pan recess on the old bikes had a slight taper, and would wedge up the adapter before it got completely screwed home. So, as a warning, there are slight differences, but it doesn't matter, as Dan has redisigned the SPOOFAK......
if you are running a stock filter, you will not see the difference either.