Tubular wheelset is a big negative, except for the maybe one in 1,000 potential buyers who could actually use them.
In order to sell, you need replace the tires with new, and have those tires professionally glued. 30 year old tubulars will feature a base tape that is disbonded from the tire casing due to age.
The last thing you want is a million dollar lawsuit because someone did a header on a 2 minute test ride on your bike.
In fact, in all honesty, you probably should not include these wheels with the bike unless:
- the buyer clearly demonstrates advanced knowledge as to what these wheels are,
- how they differ from clinchers,
- the consequences of rolling a tubular due to a poor glue job, and
- demonstrates that he or she can reglue these tires yearly - as is required for minimal safety reasons.