I remind you…Going from 9.5" ring gear axle to 10.5" ring gear axle, you'd not only need to verify the U-joint, you'll also have to verify how much farther the yoke is from the axle centerline.
When changing an 8.5 to a 9.5, the 9.5 yoke is about 3/8" farther from the axle centerline. Ideally, the driveshaft should be shortened ~3/8", but no-one does--they just cram it farther into the tailshaft housing.
And that works. That's what I did, years ago.
But I don't know how much bigger the 10.5 housing is from the 9.5 housing. I have a suspicion that it's enough bigger to require shortening the driveshaft. This is only a suspicion. Supposed to have thunderstorms starting any minute, and lasting all day tomorrow; and I'll be gone for the weekend. Remind me, and I'll take a measurement or two when I come back