Yeah it is a PITA to get the tank out on a '78. I cut the deck up aft of the removable access cover. I replaced my tank with a 52 gal tank from overtons. It took some glass work in the bilge area, but it was worth the 6 gallon increase in capacity.
http://wellcraftv20.com/community/sh...?t=7543&page=3
Here is a few pics of the job in progress.
Carl