So lets see:
Headers
ESS SC kit
Diff swap

I thinking all the extra rowing won't bother me since lots of rowing beats any auto any day unless you live in downtown NYC I guess.

Is a motor swap an option? For all that money I feel like you can source a NA motor that will make comparable power. S62/S85, LS3?

If I had extra cash I would definitely do an S62/S85 swap E53. Alpine White 3.0i with added iS fender flares, style 87s, etc

This is exactly the path I started down after I spent a LOT of time and cash on the 540i6- which I do not regret at all. But, when I found a 4.8is with 90k fewer miles for ~$15k more than than the 3.0 would sell, I had to let it go. I only regret that a little bc my neighbor's 16yr old boy has nearly killed the 3.0 in the 6 years since I sold it to them.

The thing I don't like about he motor swap idea is that I am buying a used engine. Granted, I bought my 5mt used, but it had low miles and I am familiar with the quality of it. So bolting on a new SC on it seems to be the lowest risk and also the easiest for a noob mechanic like me and it seems the easiest way to keep AWD. Maybe doing this will get me to leave my 4.6is alone and not entertain making that a RWD 6mt frankenX5.

In addition, the supercharger can be uninstalled and the X5 returned to stock. The kit can then be sold or you can put it on any M54 engine that BMW put in dang near every vehicle around that time.

- Headers
- ESS SC kit
- Diff swap
Thats my 'someday' plan as well

4.10 ratio is a lower gear ratio. Going to a 3.64 would result in slower acceleration and if the vehicle could push the wind out of the way higher top speed.

I am in the middle of removing the 3.91s in my 4.6 and replacing them with 4.10s. Rear is in place. I discussed a six speed replacement with a ZF specialist. He thought it a bad idea due to the complexity of integrating the additional computer controls.

This conversion was done on an E38 7 series. Granted, it's not AWD, but the tech and running gear of the day is pretty similar. I do not know if Brett Anderson actually put his hands on it, but something about the conversion has his name in my head for some reason. It may have been the custom driveshaft.

It was an interesting story. The E38 was called 'Baby' and the ID of the guy who did was Simeon. IIRC, he got in some pretty deep trouble over his shenanigans when he transported the car to Germany to tool around. From then, I do not think there remains much of a trace of the conversion.

Edit:
Well- it's been a few years since I looked. Baby's got a build site: Link Looks pretty limited. He does not go into the time in Germany and he does not talk about the rear window popping out in OneLap from chassis flex. Wow. The things we remember after so long...

Hey Dudes. Thought I'd hop in and share some love with guys. I'm here quite often. The 3.64 diff swap is must for any manual e53. Hands down. Squid, I'll pm you my personal info. Next time I'm in SLC (or if your up to Logan) you can drive mine. 😉 Headers, software, diff swap, etc.

I've got some things cooking that will be of... Let's say...of great interest to you all. Details will be released soon as the project materializes.

Bcred, your technically right about slower acceleration. But, in a sense, I counter that in the case of the e53, I'm faster with 3.64 diffs than 4.10s. I have more gear to wind out a high reving m54. 0-60 consists of ONE Gear change. (7k redline) The transmission has some pretty low gearing still. (1st is 5.10 or so). Coupled with software, this is a different beast. If the weather is nice, I'll take everyone on a canyon YouTube ride. I can still tow just fine, and in 6th and in the meat of the powerband she still pulls great. If I'm crusing lower rpms, a downshift accomplishes everything you want. (135 is not a big reach) At some point wind resistance becomes your enemy. Not sure where yet. But I have more head room in 4th and 5th, where a stock e53 my peter-out. Once or if the salt flats dry out, I'm going in for some legal runs. More on that later.

Waiting to see what you accomplish green dragon.