Re: 954 Wheels???
The front RC51 axle is only 22mm so you'd need to swap 25x47 bearings in and replace the centre spacer with a 25mm one - probably from your 954 wheel if you're lucky and they're the same length. Otherwise take the 51 spacer to a machinist and have him make you one exactly the same length but with a 25.25mm bore out of aluminium.
Axle spacers I would expect to have to make your own anytime you fit a different wheel.
I recommend replacing bearings anytime you swap a wheel anyway simply because they're so cheap.
"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder