It did involve some cuttin' and gruntin' but I didn't have to tear up much to get the tank out.
Inspection reveals corrosion and a few pinholes. Picture of tank bottom is posted at:
http://ph.groups.yahoo.com/group/Oday/photos/browse/e5ca
I found an interesting article concerning aluminmum
fuel tanks and how to install them properly.
http://www.yachtsurvey.com/fueltank.htm Seems that mounting them in a wooden tray as on the O'day 34 is not a good idea.
The good news is that there is a label on the tank with the manufacturer and model number. I can get a replacement tank for a bit over $300 manufactured by the original tank fabricator.