changing the spokes. Its laced onto a XM819 rim. (32 hole)

Without measuring the hub and going to the DT Swiss spoke calculator, I'd say there's a good chance it will…..

Just about. Assuming it's done 3 cross, the shimano should be using 259mm left and 258mm right spokes, and the hope would use 260mm left and 259mm right spokes.

Although there's a bit less margin for error on the spokes, you should get away with using +/-1mm different from the reccommended lengths.

Personally though if the old wheel's been in use for a while, I'd be tempted to change the spokes anyway.

Wheel is about 4 years old IIRC.

Existing hub is goosed. Had hoped to try and keep the costs down so was looking at a direct replacement.

May need to decide whether to just bite the bullet and buy a new rear wheel complete as the 819 rim does have a crack in the rim although this has not caused any issues running tubeless.

And it seems madness just to bin it!!

Its a dilemma for sure.

Just about. Assuming it's done 3 cross, the shimano should be using 259mm left and 258mm right spokes, and the hope would use 260mm left and 259mm right spokes.

If those spoke lengths are correct (And I do belive you!) than it should be absolutely fine. I recently did just this with spokes that were in theory 3mm too long, no problem at all. It built a nice tight wheel. 🙂

You can get away with too long far more than too short. You just have to be careful that the spokes don't come too far out of the back of the nipple, (a potential problem with the closed rim bed on the 819s), or that you run out of thread on the spoke.

I was taught not to reuse spokes if they had been used for a long time, and never to reuse nipples. If you're happy that the spokes are good enough, then you could save a bit by just getting hold of some new nipples.

Typically Hope hubs work fine with spokes that work on a Shimano hub.

I was taught not to reuse spokes if they had been used for a long time, and never to reuse nipples

Totally disagree. spokes from properly built wheels should last almost indefinitely. I have wheels built with 10+ year old spokes and that have been reused at least four or five times with absolutely no issues. Replacing nipples is debateable. I certainly usually reuse them as they're typically fine but if over-tensioned/twisted it's worth replacing them for the sake of an easier build.

Spokes are spot on – wheels were superbly built by Squarewheels LBS.

This is only a winter wheelset any way as I just bought pro3's for racing.

I'll leave it to the discretion of Squarewheels as they will be rebuilding it for me.

Thanks for the advice, its allowed me to make my decision.