The hesitation I would have with the 8.25 is the tendency for gear noise with 4.56 gears. You also have the issue of the stock drum brakes, which are crappy.
I built an 8.25 with 29 spline alloy shafts, 4.56 gears, Auburn, and a disc brake conversion, and I ended up selling it. I would have kept it for 35's from a strength perspective, but even after a full diff rebuild it was so noisy that it made my ears ring. Some noise is fine, hearing damage is not. Everything included, I put over $2K into that axle. You could have a custom built D44 shipped to your door for $2K, and you could get a high pinion axle custom made and shipped to your door for $2,700 (Currie HP 9").
I now run a Currie high pinion 9" and absolutely love it. It is quiet, smooth, and the extra pinion clearance is nice for rock crawling - I used to drag my 8.25 all the time. Perfect axle for 35" tires.
The thing about stock axles is that over time the only thing you keep is the housing. You will upgrade the axles, brakes, differential, and gears. A custom made, brand new housing can run as low as $300. Check Currie's website. The cost of everything else is the same, or in the case of 9" parts, may even be less expensive.
The only reason to build a stock 8.25 is that you can do it step by step vs. a one time expenditure, but from my experience, I wouldn't. Keep that 8.25 totally stock, buy a custom housing, and build up the custom axle piece by piece as budget allows, and then do the swap and sell the 8.25. The 8.25 shafts are worth $75/ea as spares to other XJ'ers.
Nay