Hawg... ALL boats of that era are subject to blistering. Those that used the fire retardent resin are almost guaranteed to have them. If a boat is hauled and dried out each season it is less prone to blistering than if it is left in the water year round.
While I strongly recommend barrier coating a boat that will be in warm water year round...it has obviously made it this far without one and there is probably little chance of extensive blistering occurring within the next 12 months.
By not doing a barrier coat now your are risking a bigger job $$$ and a drying out period should you find blisters at your next haulout...but sometimes food on the table comes first! With any luck you'll be lusting after a C34 by the time she needs further bottom work!!