In addition to the above reply, I have done alot of on-line research on replacement fuel tanks suitable to replace the original Wellcraft 60 gallon belly tanks. Most of the replacement cross linked polyethylene belly tanks made by Moeller, Todd, etc. cannot be used to replace the original 60 gallon tank unless the V20 is seriously modified or the fuel capacity of the replacement tank is seriously reduced. The reason for this is that the replacement plastic belly tanks bottoms have an angle of about 12 degrees and the V20 has a deadrise at the transom of about 23+ degrees. The angle of the V's bottom and the 12 degree angle of Moeller, Todd, Oceanlinc, would mean that any ready made belly tank over 29 gallons will not fit unless you raise the hatch about 3". The 3" would be for a 42 gallon belly tank. A 55 gallon belly tank would most likely require the hatch be raised even more. The length of these ready made plastic tanks is also a problem because most are over 45" in length and it would require modifying the bulkheads to accomodate the longer tank fore and aft. I am using my standard 84 cuddy outboard V20 as the model for below floor space. My old tank is the one shown above.
My conclusion is that if you want to have your main tank to have a 60 gallon capacity, you need to have a custom made tank fabricated to match your old tank or reduce your fuel capacity to about half. There may be a ready made tank out there that may fit better but I haven't found it. I hope this helps if you get a leaking tank and you need to replace it!
Geek
