Supra diff would actually be a good move in terms of cost.

I wouldn't put a Atlas anywhere near a Saph though LOL, at the end of the day a 3k FF Atlas still uses a OE CWP which frankly IS the weak link, people do break them in old Fords and I'd expect if you fitted one to a Saph with its extra weight you would have problems.

Danny used the Mustang 8.8 axle iirc, certainly the best option in terms of strength but its not a straight forward fit. A mate of mine has the diff for sale out of his Corvette, that has handled 800hp and 1.4 60fts at the pod so I'd say its upto the job. The only issue he had (which is why he went 9") is when using the transbrake he would occasionally snap a shaft but that is what happens when you run huge semi slicks on a prepped track.

The diff was built by Hauser Racing, I have no idea on costs or sizes but I'll ask him for you if you like