Vintage Dirt Bike Q & A

Hi
I have a pair of 87or 88 cr250/500 forks. I don't know how to tell which is which. Is there a quick easy like 1 ring at top is 1988 and 2 rings at top is 1987 ? Maybe casting number on the slider is different ?

I read the only difference inside was valving midrange...has anyone compared the dampner rods or shims to see what is the difference.
I have a 1983 CR480 and was thinking to switch the internals from these extra 87-88 forks into my 83 like I read somewhere could be done.
If switching insides isn't possible,,,I'll most likely cut off the disc brake stuff and tig weld a backing plate nub on them.

Thanks for advice and experience.
Brian riv187