Originally Posted by prairie tuber
The inside dimensions of an F470 are similar, whereas the outside dimension of an F470 are a little bigger because of a larger tube diameter. The Futura MKIII appears to taper towards the bow more that the F470 does.
You may want to try to find out the exact dimensions of the keels to make sure that they would be interchangeable. If the maximum girth of the keels are different, you would end up with either loose/sloppy floor fabric or excessively tight floor fabric.
Zodiac Nautic - Boats - Futura Mark III Alu
For the post 2004 boats, you are correct.
1982 through 1986, the hull design was the same as the FC470. It was actually hypalon/neoprene as well, I believe it switched to PVC in about 1984 or 1985. This is what I quoted the Z3031 keel from.
1987 , still PVC, the bow was changed and the boat narrowed. This was the basic hull design that carried through until about 2003.
2004 through present, the tubes were truncated and the boat widened thanks to the increased tube diameter. The change was brought on by 4 stroke outboard necessitating more floatation to optimize outboard performance.
See picture...look familiar?