front wheel puzzle

Neither the wheel or the forks are off a Navigator. They look to me like they are from a Jubilee.

From your pictures it looks like the last style of fork down tubes for a Jubilee (after Plumstead move & square bottomed) with the earlier style fork shrouds/top yoke and an earlier style of front hub for a Jubilee (pre Plumstead) which is a "slip in" type for earlier down tubes. The hub won't fit the later down tubes as they use a standard type through axle bolt - I don't think the two types are interchangeable - at least I never managed to make an earlier hub fit the later forks!

Also from the pictures, the RH lower slider should be the other way round with the"boss" facing inward as this acts as the brake backplate locator

Others will come along with better info on serial number changes etc - good luck with finding "correct" year parts for the front end, they do come up from time to time but I found getting the correct later front hub a bit of a nightmare, but earlier parts are more common - it's going to depend on how accurate you want the Jubilee (if it is a Jubilee) to be, based on its year & serial number!

However, if the engine is the 350 Navigator and matches the frame number then both forks and front wheel are totally wrong and should have the Roadholder style forks and larger front hub (been there) and had to get correct items to suit the Jubilee - all depends on what you want to achieve in the finished build!

Good luck - Bruce

... that the Navigator (and Electra) forks and wheel are essentially short Roadholders as fitted to the heavy twins (apart from having slightly lighter springs), which will widen your search opportunities.

For what it's worth, I hate those Francis-Barnett type forks. I rebuilt a FB Cruiser a few years ago and really didn't like the design.

Funnily enough my Jubilee came with roadholders, which is why I bought it! 

... about the first one. The second one would fit with short roadholders - I'd be looking for something like
https://www.ebay.co.uk/itm/226918416734

By the way, if you include the url in your post by using the little chain symbol in the icons above the post it's clickable without having to copy & paste it. Like I did here.
 

The only main difference between a Navigator and jubilee frame is the head steady mounting (and engine/frame number of course!). 

Andy will know for sure but i think you can convert the hub, Ive just been looking at mine, I have a fixed axle hub which I was going to change to a "through axle"  like you need, but I bought a pair of NOS sliders from the club which are the older fixed style.  So I can use the original axle.  As far as I can see the bearings are the same size and the spindle end is the same size as one of the  sleeve nuts, so from a quick glance, you should be able to make the wheel fit if you make a spacer for the non brake side. I have just noticed that my straight through spindle has a step in it, which stops the spindle going in far enough, assuming mine is right, that might need turning off on a lathe. 
Dan 

This is a good read 
https://www.nortonownersclub.org/forum/jubilee-front-wheel-spindle