It could be done
Try and find a diff may be a borgwarner thats the same length then weld, cut,grind your original brackets into place
Remove front drive shafts , custom tailshaft
Cross your fingers for rego time if they dont spot it may need engineers certificate
As I told you via PM. Your just going to break stuff. If you put a borgwarner rear diff and appropriately stronger axles you will just find the next weak point which is the transfer case which can't be substituted for anything else. wanna do skids get a skyline/falcodore or just learn to spin 4 tyres instead of 2.
Did it with a 7th gen VR4 years ago, all I broke was the rear diff casing, aluminium part at the back of the diff snapped where it mounts to the sub frame. Weld up the centre diff and remove the front axles. Did pretty good skids