Here is what I found out Nort, since I had time before the sun came up and was up anyway.
I looked on Yachtworld.com for Sunseekers for sale in those years in order to find Registration names and then cross referenced them to the USCG Vessel registration search... here http://www.st.nmfs.noaa.gov/st1/CoastGuard/index.html
I could not find a documented Sunseeker for 1994, I did find the following.
Sunseeker 1993 HIN# XSK19360D393
Sunseeker 1993 HIN# QSU3045252002193
a bunch of 1996 with all the HIN starting with "SUN"
As of late (ie 2005 and above) the HIN I could find start with "HSK"
My bet is in those years Sunseeker might have a bunch of variables relating to the HIN numbers if the Company was changing hands and being run under different Corporate entities.
I would try to get a hold of a Sunseeker company rep or a dealer that knows his azz form his elbow and get a letter stating that this was the HIN numbers used in those years. They still might have record in England. The other avenue would be contact a surveyor like our resident expert Ed Cozzi (954-895-4633) and you might be able to get a letter from him stating the CURRENT market value of your boat and then fight your Governmental entity assessing your ride erroneously. The surveyor might also be able to document/explain officially your HIN issues.
That would be the road I go down anyway.
Just my enormously humble opinion...
Ever your servant...