Hmmm, one way to find out would be to get PHS documents. But then it may show the Y88 as a t-top, we don't know what a PHS for a hardtop Y88 would look like (assuming it even exists). Do you have any documentation on it? A roof swap could be likely, someone a long time ago could have gotten sick of leaking t-tops and swapped the roof.
hada76, remember, the t-top delete SE was in 77 and 79, there is no known t-top delete SE in 78.