[johnnywalker]

Thanks much for the info and suggestions,

Here's what we have so far:

There is no foam on the sides, we can get all the way down the sides to feel no foam, very tight but enough room to know there is nothing holding the tank in on the 4 sides. There is something holding the tank down from the bottom, feels like it is some epoxy, glue or foam coming from the front or back o
f the tank or put there in purpose to hold down the tank.
I have a block and tackle coming next week I had on order for Tuna and the boat has a pretty solid hardtop that we may be able to use to hoist up the tank. The tank is currently 1/2 full of fuel that has been there for many years.

The boat is in Weymouth

leaning towards the 5.7 unless I can be convinced off a better way to go

What about the duo prop option with Merc or Volvo's? Anyone go this route or have an opinion?

Few more pics