Congratulaions on this project turning out so successful! It would have been really crummy if after all that you couldn't tell the difference between the 3 and 4 blade props. Sounds like they are really a winner, and now you know exactly what you have aft of the trannies.
As to cost, you would have had to pull the boat for hull painting sooner or later anyway, so the truck rental and hull cleaning/paint work can all be chalked up to that part of the work, making the new shafts and props a lot cheaper!
Best wishes,
Curt....
1967 fiberglass 38' Chris Craft Commander Sportfisher with twin 427 CID 300 HP engines.