I have 3 SQL Server 6.5 books gathering dust in my garage...
The SQL Server 6.5 Performance Tuning and Optimization guide by Ken England
Planning and Building a high performance database by Robert D Schneider
SAMS SQL Server 6.5 Programming Unleashed
I don't know if these are any good to you. I'm not looking for any money for them (other than to cover postage). Of course, postage may be too expensive, depending on where you're based. I'm based in the UK.
PM me if you are interested.