Is an 8 1/4", 2.45:1 diff housing exclusive?

I run a 2.45 housing that was converted to a 3.21 SG using the pinion, ring and carrier from my 84 D150. I had the work done at a transmission shop that knew their way around 8.25 rears. After 3 weeks it was ready and the mechanic was not amused - it was tougher than he figured. Been driving it for over 7 years.