Hi Rob and welcome to the forum.
You have got a very interesting car there, the 1639th FE built, which means probably late July or early August 1956. Do you still have the original engine number?
There is a good reason why the paint numbers don't compute with the ID decoding page - they're FJ format! The leading digit (always "1") was dropped from the BALM codes put on the FE ID plates, so plug 7447 and 7449 in and you'll get the answer, or
check here and you'll see they are indeed the paint colours for Breton Blue and Cabot Grey, which sounds like a very nice paint combo, BTW.
In early 1957 GM-H did a serious reworking of the body strengthening of the FE, adding a variety of gussets and ribs around the rear window and dog-leg to correct problems with unacceptable body-flex in real early vehicles, that led to back windows falling out, doors not lining up properly etc. With that serious mumbo you're planning for the car, obviously you're going to have to put a chassis in it, but you should probably have a look at the work that was done by Holden to strengthen other bits of the car. I've got a copy of it if you're interested. Always happy to help another '56 owner (mine is #5678, early September
)
What part of the world are you in?
cheers
RET