That is precisely the reason why. He was going to try and use the OE EFI system which I also removed from the M3. The more I dug into my car and researched the cars electrics after removing the engine and EFI, the more I found that the BMW EWS-II system, (BMW's antitheft system post '96), is a nightmare to work with. There is an antenna in the ignition switch that reads the chip embedded in the key. The key is "matched" to the BMW ECU which is electronically/digitally "aligned" to the EWS-II module, separate of the EFI ECU. When an ECU dies, getting a new one installed requires the dealership to realign the ECU or it wont run! In short, Ron would need one of my keys, (more on that below), an antenna from a BMW ignition switch surround, the EWS-II module from my car, (which also has my control control integrated into it), and a few other hurdles to jump through. The pre '95 cars with the EWS-I are not as intricate, but still use the same key/antenna thing.
Regarding the BMW keys, as I understand it, (I could be wrong on this as the info is hodge podge of book and internet crap I read and based on my experience acquiring a spare key, I believe it could be true). BMW produces a set number of extra keys for each and every E36 that rolled of the assy line, a couple go with the car, the rest are put into a vault of sorts. If you want/need a new key you have to go through BMW, you can't just have a key made at any locksmith. When I bought my M3 it had only one key. I went to BMW to get another one, had to present my drivers license and vehicle registration to prove ownership, (photocopied and sent to BMW NA office), then took my $70 and 3 weeks later I was able to pick up my spare key from the BMW parts counter.