Well, I suppose if the newer (S54 engine) will be used in an older-gen car, the backdating may be ....reasonable....and meeting emissions regs & stuff for an OBDI car, or older, will be doable in that case. Will definitely need someone who is comfortable with the electronics/software/firmware on these vehicles. Most importantly how the various modules interact with one another.
Plug & Play? Sure, as long as you have top-notch resources from which to draw. Else it'll be Plug & Pray.
My experience "dropping" the S54 into my E46 wagon was, well, more challenging than expected. Mechanical stuff (my expertise
) was a breeze. As Ben Liaw @ Rogue documented (props to Ben for his advice on my project
), everything pretty much bolts right in. That's the easy part. Making the M3 DME and associated M3 modules work together in a non-M vehicle is a challenge unless you have unlimited funds and can just change everything on a whim, or really, really, know what you're doing.
Remember that the DME, LKM, EWS, Ignition key, Body Control module and Gauge cluster all "talk" to one another over the CAN bus and so must think they belong together (ie. from the same vehicle). They look for S/N and mileage data stored in memory across themselves and it needs to cross-check. Otherwise, no start, or start with CEL's, poor running, etc. Some of this can be taken care of by "re-alignment" of the various units via the GT-1 or MODIC. Some not. Buying "uncoded" modules on a trial and error basis adds up to big $$ quickly. Burning a new "uncoded" DME with the wrong firmware is a $1000 screw-up. Oh, there are now 15 or 20 M3 DME p/n's to choose from in the BMW parts catalog. Trying to figure out which one you need can become a costly exercise. You can make $1000 paperweights in a hurry with one coding error on the GT-1. Then you have to figure out how to deal with signals (read: wires & connectors) that the M3 is looking for that don't exist on the transplant chassis & vice-versa.
So if you are electronically savvy in general and modern automotive CAN-bus system savvy particularly, have access to the specialized BMW diagnostic tools & equipment and to factory service data you can pull it off. Not impossible, but tricky. Far, far from "just drop it in" as so many here seem to think.
Beyond awesome when done of course.