Ive been playing around with the idea of getting some new (to me) wheels that are ment for an e46. 18" or 19" i dont know, 18's would be smarter.

What kind of spacers would i need to pull this off?

I'm assuming your putting these wheels on ur 89' m3. it all depends how big your tires are, what size tires do you have? I have put a set of 18mm spacers with 225/40/17 tires and they work perfect. Some slight rubbing on the front wheels but my m3 is lowered.

I suggest you go with 18's because our cars weren't really made to go with 19's. I haven't seen anyone yet with 19's so its your choice. I have 17's and look and work perfect. Smaller size wheels will give you better performance.

18” are a hypothetical. I was wondering what spacers I would need to run an e46 offset but now I realize how general that question is. I guess im just wondering if I can even pull off an e46 type of offset?

I have seen two guys pull of 19” with like 225/35 I THINK. Honestly I don’t want to go 19” because there’s to big a trade off in every aspect.
Right now im running 235/40/17 and they are perfect with no spacers on a 5 series offset.

just curious, what kind of wheels are they? and what is the length of an e46 type of offset?

I think they are CSL. Its one of the guys on s14. Ill check when its back up.
Dosent look cartoonish like you would think.

Im tempted by stuff like this...
http://forum.e46fanatics.com/showthread.php?t=436499
or some senekas. Ok ....so im vain...so what..lol
I think 18" is perfect though.

If you are talking about Ryan's car with the 19" CSLs, they look great, but I read that he had to do some bodywork to get them to fit.

Pulled and rolled im guessing? Sounds like scattered, covered and smothered......
Yep i think its Ryans car im talking about.