You will be hard pressed to find a wrecked Prado with 4.1's
Nitro is out of stock of 4.1's globally until the new year.
The N80/N70 front housing is the same except the usual 3.9 and up and 3,7 and down equation which require different centres.
I'm not sure about swapping the rear N80 diff lots to consider there. The leaf springs are different, they run different gearboxes so the tailshaft lengths are probably different.
The content of this bible I wrote circa 2010 has mainly moved to
https://www.vmn.com.au/ where some of the tables can be better formatted. Refer to our resource centre on that site.
Long and the short, best ratio for all tyre sizes 32"and up is the 4.1. At 35's the 4.5s are the best match.
The Nitro gear sets are "thick" cut so will fit the standard Hilux N70 centre. Most often though people will fit a Harrop elocker while they are apart. They also have been hard to get stock of. We have some in stock and have generally been able to fill orders even when Harrop are out of stock.
We have a number of Nitro 4.1's on backorder so feel free to join the queue. We expect to have stock before the Aussie distributor via airfreight instead of sea.