The short adapter is the novak kit. It is the one I have as well. The statement about the transfer case being weak until their input gear is installed is a little bit of a stretch. The gear that is provided with the novak kit comes from novak although is not made by them only modified by them and is of no higher structural quality. If anything I would say its weaker for reasons that would take a while to explain and drag the novak name through the mud a tad. Its been established already that this t-case can handle that kind of power without mods. Motech isn't doing any special magic here.
The weak link is the small input in the 241J to match the small output of the NSG and 42RLE. In the early days we saw the small output shafts of the 4l60's twisting under the power of a 6 liter engine. The 4l65 was a good transmission behind small blocks and other V8's but when strength was required you needed to step up to the 4l80, esprcially with large tires that grab and don't spin. The larger LS's like the 6.2's went to the 6l80 which shares the larger output shaft of the 4l80 to handle the additional torque. A 6.0 engine in stock trim can put out near 400 ft pounds of torque and a 6.2 well over 400. The small input in the 241J was the weak point. I had one customer break an output shaft on a 4l65 with a 6.0 so he purchased a custom hardened output shaft and twisted that.
Some Hemi guys have good luck running the J behind the Chrysler transmission but we found from experience going to the large input makes the 241J hold up to 450-500 HP on the street(in reality it's not so much the gear as the larger OS). Remember we have done hundreds of conversions and this is our experience over many years.
We like and work with Novak all the time. I believe Novak is now outsourcing the input gears and they are imported but we never had a problem when we used them. The Novak adapter uses two horizontal studs to support a somewhat thin "L" bracket which mounts a rather small poly transmission mount. Early on we used the Novak adapter because it was shorter than our full size adapter to get better DS length. We replaced the small "L" bracket(as you know) with a larger stronger "L" bracket to support the full size HD GM 2 stud 4x4 mount.
I still prefer our full size clocking ring with the transmission mount bolting horizontal to the adapter, the same way GM does it. On very high HP builds I feel the direct bolt method is stronger than the cantilevered "L" bracket with the small poly mount.
If converting a 2WD 6l80 to a 4WD you may have an issue with the Novak adapter since it is shorter and some of the 6l80 output shafts are not splined far back enough. You can run a short input gear or a .5" spacer but it's easier to run the full size adapter which is the same size as the stock TC GM adapter.
We don't have any magic just experience, we have been doing LS JK swaps since 2009.
I do agree with the above statement about the gear vs chain TC on the street. The geared TC's run heavy gear oil, have critical tolerances, can be slightly noisy, need to warm up, hard to shift... where the chain case runs ATF, an oil pump, is quiet... But when it comes to off road the A2 has many advantages which make it worth having. In addition I know Advance is improving the A2 right now to make it even better.