I'm also fairly certain there have been some other homebrew/Sloppy Mechanic E90 LS swaps, one turbo'd if I recall. I think he even did his own 8.8 swap.
If this swap kit is priced the same as most of their other ones, you could probably do a LS swap, use a CD009 transmission instead of a T56 to save some cash and put a turbo on it and have a really cheap fast car. Maybe not a good candidate for a 335, but for a 328...
I figure he must still have it. He has a build thread on LS1tech. His most recent post said it broke the axleshafts on the dyno at TX2K. He said it made 687HP @ 13psi. I can post the link if that's ok.
Dude is a fabricator that's for sure. Made his own axleshafts from 4340.
I don't know that I have heard of a CX Racing swap kit that went in without significant fitment issue and I have seen a few on a couple of platforms. What are they doing for engine management an gauges?
I don't think CXRacing goes beyond physical installation. As for gauges, I think everyone might be overthinking CANBUS. The picture that I attached (why the hell its not a large picture is beyond me - i cant figure out this millenial forum stuff) is not a CXRacing setup. A guy on LS1tech did his 3 years ago and he said he is using an MS3 computer that can inject the tach signal at the stock crank signal. He said the speedo is run off the ABS so it works fine. He said all other interior items worked fine.
He said he might be offering his brackets for an 8.8 as well (have to figure out axles on your own) but might be a good value option for an LSD.
LS1 dressed is around 430lbs, N54 dressed is the same. With all the turbo hardware the n54 is probably a little heavier all said and done. The LS will undoubtedly fit better and push the weight lower and more central.