IMHO running and diff upside down from its designed orientation is not a good idea
I have seen an add on perch like this, no welding involved. would get you about 3.5" PLUS the thickness of the spring pack.
This image is for lowering but would work in reverse as well
View attachment 1716466869
THAT BEING SAID...
As previously noted the pinion angle would be all wrong, and if an 8 3/4, the housing is not very stout (7 1/4 would be stouter)
It sits on and in the lower perch and the U bolts hold it to the axle housing. you would need upper and or lower mounts to do this.