For a few years now I've just thought to myself "hey...LS swap the thing and be done with it" which all sounds good and is easy to say. But after giving it a lot of thought and knowing that I now have a reliable and fair specialized BMW mechanic less than a mile away...I'm wondering if maybe I should stick with the M54 motor.
Please don't take this the wrong way, but if being near a good mechanic might influence your decision, and you want the car to last forever, I don't think you want this to be an LS swapped BMW. It obviously can be done but it's not the kind of thing that's going to yield an, erm, OEM+ result.
Before you ask "what do you want the car to do?" I want it to go fast and I wanna have fun. It'll be a street legal car that I take to the track that retains most if not all factory creature comforts. I want it to be balanced but also make people laugh and maybe scared a little bit. I want the car to last forever.
Thanks for this. So many people leave it open ended and then the replies just describe cars they would want. This is a reasonable build we can shoot for. Some thoughts:
Spec E46 suspension kits are $5k.
The problem is that that's not street/track, it's full on racecar. Something like 800lb springs and damping that's set up for a car weighing hundreds of pounds less. On the street the car would neither ride nor drive right. You'd likely be much happier with something like KWs, or ideally, Ohlins. Camber plates I also would not mess with unless you're getting weird tire wear at the track.
Manual transmissions are abounds.
Do it. There's plenty of guides for E46 M3 SMG conversions, it won't be exactly the same obviously but stuff like clutch pedal and mounting points and stuff will be a good reference for you.
I keep thinking about how nice it would be to have a built NA straight 6 that IMO sounds better than the S54, and kinda keeps the spirit of the car alive. But then I get swayed by thinking about doing huge burnouts and having something absurd to play around with.
If you want to LS swap
something for all those smoky burnouts let it be a dedicated project car you don't have an emotional attachment too. Maybe a hooptie E36 you find cheap somewhere. S54 is the only logical swap I can think of here for street/track/longevity as the chassis and such were designed to accommodate it so it's mostly finding parts as opposed to making them.
Another point, the rear subframe/chassis is liable to crack on these with hard use, it may already have. It can be welded and various companies make reinforcement kits.