1989 23WA Seacraft fuel tank replacemnt/maybe?

[gss036]

Stopped by a shop that makes tanks for all the local boat builders. Got an estimate of about $500.00(ballpark)for a 65 gallon tank.
Should I put a larger tank back into the boat or go smaller. How would it hurt future selling price. Around here most boats this size run around 60 gallons.
Next project is going to be removing the deck plates and do a closer inspection and a look into the tank.