Having dealt with more than a few walnuts...
To help you decide how to cut it, start by cutting a core from the tree to see how much sapwood is there before the heartwood. Different cultivars in exactly the same conditions will maintain widely variable amounts of sapwood. Three feet of diameter guarantees there will be enough heart in the center to hide quite a few blanks. Even if you just trim some sapwood off the outside to see how deep the color is you will learn plenty.
There are a lot of good blanks in the tree regardless the "overall character" of the wood and the rootball is important as many have said.
The iron is an issue and I have some scars to explain why... It is why you will probably be forced to chainsaw it...
Do NOT attempt to use any limbs for lumber and especially not for blanks. It is 100% firewood due to juvenile and other reaction wood types.
If it has black marbling (quite possible because it looks like there is some insect damage and the lopped off branches allowed fungal access) boardsawn is going to show better. Curl is shown much better when quartersawn.
In the second photo the cut-off branch stub has a slight V in the bark immediately under the branch. That bark died as a result of the branch being cut off. There was some growth for awhile after the branch was removed and there is a ridge of figure directly behind that V extending deep into bole-branch junction. There may be progressively smaller ranks of Vs inside the first... May be a couple outside the line, too. A boardsawn series of 2-piece blanks right there will look pretty good, especially if cut long on the top end (about the center of the limb).
The other, more standard cut for limbs to achieve feather or crotch figure (same thing) is quarter-sawing starting with a cut straight through the center of the tree and the branch. So the centers of the them form a "Y" on the cut surfaces.
In the last picture, under the large limb there is obviously some curly stuff right there in the tightest turn, also, below and left of it there is what appears to be a high spot in the valley of buttressed wood and the main bole, with some curl clearly telegraphing through the bark.
Have to go pick up some bear hunters, but will add more later... Especially in regards to the roots.
art
