will a 3/4-1ton 9.25ifs differental assembly fit in a 1/2ton 4x4 1998 tahoe? Is there any differences between the cases,mounting location,axle flange and driveshaft yoke.
your information will be helpful

eveything is different, mounting, frames, etc. I dont think any of the parts fit from 1/2 to 3/4 ton.

This idea has been played with before.
The quick and simple answer is it cant be done, just go get a one ton.
Having been said.
Where there is a will there is a way, so yes it can be done. But it is no where as simple as your thinking to just replace your half ton diff with a one ton and bolt it in. It will require extensive modifications to the point where it is much easier to just buy a one ton pickup. Now at days the trucks can be picked up very cheaply so it isnt worth your time to do the mods to your existing truck.
Besides, if were a feesable modification, the after markets would have been selling kits for it.
You can find all kinds of kits for your truck, you can even find SAS kits for your truck but I dont think anyone makes a one ton IFS conversion. If you do it, post it up.